diff --git a/src/LegacyCallHandler.tsx b/src/LegacyCallHandler.tsx
index a592c3b055..f8096ae561 100644
--- a/src/LegacyCallHandler.tsx
+++ b/src/LegacyCallHandler.tsx
@@ -652,9 +652,9 @@ export default class LegacyCallHandler extends EventEmitter {
     }
 
     private onCallStateChanged = (newState: CallState, oldState: CallState | null, call: MatrixCall): void => {
-        if (!this.matchesCallForThisRoom(call)) return;
-
         const mappedRoomId = this.roomIdForCall(call);
+        if (!mappedRoomId || !this.matchesCallForThisRoom(call)) return;
+
         this.setCallState(call, newState);
         dis.dispatch({
             action: "call_state",
diff --git a/src/audio/PlaybackClock.ts b/src/audio/PlaybackClock.ts
index 1a6d1a2e5d..6775c09fca 100644
--- a/src/audio/PlaybackClock.ts
+++ b/src/audio/PlaybackClock.ts
@@ -60,7 +60,7 @@ export class PlaybackClock implements IDestroyable {
     private stopped = true;
     private lastCheck = 0;
     private observable = new SimpleObservable<number[]>();
-    private timerId: number;
+    private timerId?: number;
     private clipDuration = 0;
     private placeholderDuration = 0;
 
diff --git a/src/audio/VoiceMessageRecording.ts b/src/audio/VoiceMessageRecording.ts
index 7d5c491261..b46fd0da23 100644
--- a/src/audio/VoiceMessageRecording.ts
+++ b/src/audio/VoiceMessageRecording.ts
@@ -33,9 +33,9 @@ export interface IUpload {
  * This class can be used to record a single voice message.
  */
 export class VoiceMessageRecording implements IDestroyable {
-    private lastUpload: IUpload;
+    private lastUpload?: IUpload;
     private buffer = new Uint8Array(0); // use this.audioBuffer to access
-    private playback: Playback;
+    private playback?: Playback;
 
     public constructor(private matrixClient: MatrixClient, private voiceRecording: VoiceRecording) {
         this.voiceRecording.onDataAvailable = this.onDataAvailable;
diff --git a/src/audio/VoiceRecording.ts b/src/audio/VoiceRecording.ts
index 033c5da475..2e1f5634fb 100644
--- a/src/audio/VoiceRecording.ts
+++ b/src/audio/VoiceRecording.ts
@@ -243,7 +243,7 @@ export class VoiceRecording extends EventEmitter implements IDestroyable {
             return;
         }
 
-        const secondsLeft = TARGET_MAX_LENGTH - this.recorderSeconds;
+        const secondsLeft = TARGET_MAX_LENGTH - this.recorderSeconds!;
         if (secondsLeft < 0) {
             // go over to make sure we definitely capture that last frame
             // noinspection JSIgnoredPromiseFromCall - we aren't concerned with it overlapping
@@ -259,7 +259,8 @@ export class VoiceRecording extends EventEmitter implements IDestroyable {
     /**
      * {@link https://github.com/chris-rudmin/opus-recorder#instance-fields ref for recorderSeconds}
      */
-    public get recorderSeconds(): number {
+    public get recorderSeconds(): number | undefined {
+        if (!this.recorder) return undefined;
         return this.recorder.encodedSamplePosition / 48000;
     }
 
diff --git a/src/components/structures/IndicatorScrollbar.tsx b/src/components/structures/IndicatorScrollbar.tsx
index 54d70add77..ce60ffc751 100644
--- a/src/components/structures/IndicatorScrollbar.tsx
+++ b/src/components/structures/IndicatorScrollbar.tsx
@@ -44,7 +44,7 @@ export default class IndicatorScrollbar<T extends keyof JSX.IntrinsicElements> e
     IState
 > {
     private autoHideScrollbar = createRef<AutoHideScrollbar<any>>();
-    private scrollElement: HTMLDivElement;
+    private scrollElement?: HTMLDivElement;
     private likelyTrackpadUser: boolean | null = null;
     private checkAgainForTrackpad = 0; // ts in milliseconds to recheck this._likelyTrackpadUser
 
@@ -85,6 +85,7 @@ export default class IndicatorScrollbar<T extends keyof JSX.IntrinsicElements> e
     }
 
     private checkOverflow = (): void => {
+        if (!this.scrollElement) return;
         const hasTopOverflow = this.scrollElement.scrollTop > 0;
         const hasBottomOverflow =
             this.scrollElement.scrollHeight > this.scrollElement.scrollTop + this.scrollElement.clientHeight;
diff --git a/src/components/structures/LegacyCallEventGrouper.ts b/src/components/structures/LegacyCallEventGrouper.ts
index 0fcb91992f..354116009b 100644
--- a/src/components/structures/LegacyCallEventGrouper.ts
+++ b/src/components/structures/LegacyCallEventGrouper.ts
@@ -73,7 +73,7 @@ export function buildLegacyCallEventGroupers(
 export default class LegacyCallEventGrouper extends EventEmitter {
     private events: Set<MatrixEvent> = new Set<MatrixEvent>();
     private call: MatrixCall | null = null;
-    public state: CallState | CustomCallState;
+    public state?: CallState | CustomCallState;
 
     public constructor() {
         super();
diff --git a/src/components/structures/LoggedInView.tsx b/src/components/structures/LoggedInView.tsx
index 141f61937d..85f73ee8e7 100644
--- a/src/components/structures/LoggedInView.tsx
+++ b/src/components/structures/LoggedInView.tsx
@@ -96,10 +96,10 @@ interface IProps {
     autoJoin?: boolean;
     threepidInvite?: IThreepidInvite;
     roomOobData?: IOOBData;
-    currentRoomId: string;
+    currentRoomId: string | null;
     collapseLhs: boolean;
     config: ConfigOptions;
-    currentUserId: string;
+    currentUserId: string | null;
     justRegistered?: boolean;
     roomJustCreatedOpts?: IOpts;
     forceTimeline?: boolean; // see props on MatrixChat
@@ -131,10 +131,10 @@ class LoggedInView extends React.Component<IProps, IState> {
     protected readonly _roomView: React.RefObject<RoomViewType>;
     protected readonly _resizeContainer: React.RefObject<HTMLDivElement>;
     protected readonly resizeHandler: React.RefObject<HTMLDivElement>;
-    protected layoutWatcherRef: string;
-    protected compactLayoutWatcherRef: string;
-    protected backgroundImageWatcherRef: string;
-    protected resizer: Resizer;
+    protected layoutWatcherRef?: string;
+    protected compactLayoutWatcherRef?: string;
+    protected backgroundImageWatcherRef?: string;
+    protected resizer?: Resizer;
 
     public constructor(props: IProps) {
         super(props);
@@ -200,10 +200,10 @@ class LoggedInView extends React.Component<IProps, IState> {
         this._matrixClient.removeListener(ClientEvent.Sync, this.onSync);
         this._matrixClient.removeListener(RoomStateEvent.Events, this.onRoomStateEvents);
         OwnProfileStore.instance.off(UPDATE_EVENT, this.refreshBackgroundImage);
-        SettingsStore.unwatchSetting(this.layoutWatcherRef);
-        SettingsStore.unwatchSetting(this.compactLayoutWatcherRef);
-        SettingsStore.unwatchSetting(this.backgroundImageWatcherRef);
-        this.resizer.detach();
+        if (this.layoutWatcherRef) SettingsStore.unwatchSetting(this.layoutWatcherRef);
+        if (this.compactLayoutWatcherRef) SettingsStore.unwatchSetting(this.compactLayoutWatcherRef);
+        if (this.backgroundImageWatcherRef) SettingsStore.unwatchSetting(this.backgroundImageWatcherRef);
+        this.resizer?.detach();
     }
 
     private onCallState = (): void => {
@@ -274,7 +274,7 @@ class LoggedInView extends React.Component<IProps, IState> {
         if (isNaN(lhsSize)) {
             lhsSize = 350;
         }
-        this.resizer.forHandleWithId("lp-resizer")?.resize(lhsSize);
+        this.resizer?.forHandleWithId("lp-resizer")?.resize(lhsSize);
     }
 
     private onAccountData = (event: MatrixEvent): void => {
@@ -645,7 +645,11 @@ class LoggedInView extends React.Component<IProps, IState> {
                 break;
 
             case PageTypes.UserView:
-                pageElement = <UserView userId={this.props.currentUserId} resizeNotifier={this.props.resizeNotifier} />;
+                if (!!this.props.currentUserId) {
+                    pageElement = (
+                        <UserView userId={this.props.currentUserId} resizeNotifier={this.props.resizeNotifier} />
+                    );
+                }
                 break;
         }
 
diff --git a/src/components/structures/MatrixChat.tsx b/src/components/structures/MatrixChat.tsx
index cdecf9f61e..9932a102ef 100644
--- a/src/components/structures/MatrixChat.tsx
+++ b/src/components/structures/MatrixChat.tsx
@@ -231,7 +231,7 @@ export default class MatrixChat extends React.PureComponent<IProps, IState> {
     private focusComposer: boolean;
     private subTitleStatus: string;
     private prevWindowWidth: number;
-    private voiceBroadcastResumer: VoiceBroadcastResumer;
+    private voiceBroadcastResumer?: VoiceBroadcastResumer;
 
     private readonly loggedInView: React.RefObject<LoggedInViewType>;
     private readonly dispatcherRef: string;
@@ -441,7 +441,7 @@ export default class MatrixChat extends React.PureComponent<IProps, IState> {
         window.removeEventListener("resize", this.onWindowResized);
 
         this.stores.accountPasswordStore.clearPassword();
-        if (this.voiceBroadcastResumer) this.voiceBroadcastResumer.destroy();
+        this.voiceBroadcastResumer?.destroy();
     }
 
     private onWindowResized = (): void => {
@@ -1935,7 +1935,7 @@ export default class MatrixChat extends React.PureComponent<IProps, IState> {
     private setPageSubtitle(subtitle = ""): void {
         if (this.state.currentRoomId) {
             const client = MatrixClientPeg.get();
-            const room = client && client.getRoom(this.state.currentRoomId);
+            const room = client?.getRoom(this.state.currentRoomId);
             if (room) {
                 subtitle = `${this.subTitleStatus} | ${room.name} ${subtitle}`;
             }
diff --git a/src/components/structures/ScrollPanel.tsx b/src/components/structures/ScrollPanel.tsx
index 8fc232774e..61279cffb3 100644
--- a/src/components/structures/ScrollPanel.tsx
+++ b/src/components/structures/ScrollPanel.tsx
@@ -179,7 +179,7 @@ export default class ScrollPanel extends React.Component<IProps> {
     };
     private readonly itemlist = createRef<HTMLOListElement>();
     private unmounted = false;
-    private scrollTimeout: Timer;
+    private scrollTimeout?: Timer;
     // Are we currently trying to backfill?
     private isFilling: boolean;
     // Is the current fill request caused by a props update?
@@ -189,8 +189,8 @@ export default class ScrollPanel extends React.Component<IProps> {
     // Is that next fill request scheduled because of a props update?
     private pendingFillDueToPropsUpdate: boolean;
     private scrollState: IScrollState;
-    private preventShrinkingState: IPreventShrinkingState | null;
-    private unfillDebouncer: number | null;
+    private preventShrinkingState: IPreventShrinkingState | null = null;
+    private unfillDebouncer: number | null = null;
     private bottomGrowth: number;
     private minListHeight: number;
     private heightUpdateInProgress: boolean;
@@ -234,7 +234,7 @@ export default class ScrollPanel extends React.Component<IProps> {
         // skip scroll events caused by resizing
         if (this.props.resizeNotifier && this.props.resizeNotifier.isResizing) return;
         debuglog("onScroll called past resize gate; scroll node top:", this.getScrollNode().scrollTop);
-        this.scrollTimeout.restart();
+        this.scrollTimeout?.restart();
         this.saveScrollState();
         this.updatePreventShrinking();
         this.props.onScroll?.(ev);
@@ -725,7 +725,7 @@ export default class ScrollPanel extends React.Component<IProps> {
     // need a better name that also indicates this will change scrollTop? Rebalance height? Reveal content?
     private async updateHeight(): Promise<void> {
         // wait until user has stopped scrolling
-        if (this.scrollTimeout.isRunning()) {
+        if (this.scrollTimeout?.isRunning()) {
             debuglog("updateHeight waiting for scrolling to end ... ");
             await this.scrollTimeout.finished();
             debuglog("updateHeight actually running now");
diff --git a/src/components/structures/UserMenu.tsx b/src/components/structures/UserMenu.tsx
index 5d2ba897ba..609bcdf3e4 100644
--- a/src/components/structures/UserMenu.tsx
+++ b/src/components/structures/UserMenu.tsx
@@ -88,9 +88,9 @@ export default class UserMenu extends React.Component<IProps, IState> {
     public static contextType = SDKContext;
     public context!: React.ContextType<typeof SDKContext>;
 
-    private dispatcherRef: string;
-    private themeWatcherRef: string;
-    private readonly dndWatcherRef: string;
+    private dispatcherRef?: string;
+    private themeWatcherRef?: string;
+    private readonly dndWatcherRef?: string;
     private buttonRef: React.RefObject<HTMLButtonElement> = createRef();
 
     public constructor(props: IProps, context: React.ContextType<typeof SDKContext>) {
diff --git a/src/components/structures/auth/Registration.tsx b/src/components/structures/auth/Registration.tsx
index 045ee6fccf..d8fd848320 100644
--- a/src/components/structures/auth/Registration.tsx
+++ b/src/components/structures/auth/Registration.tsx
@@ -125,7 +125,7 @@ interface IState {
 export default class Registration extends React.Component<IProps, IState> {
     private readonly loginLogic: Login;
     // `replaceClient` tracks latest serverConfig to spot when it changes under the async method which fetches flows
-    private latestServerConfig: ValidatedServerConfig;
+    private latestServerConfig?: ValidatedServerConfig;
 
     public constructor(props: IProps) {
         super(props);
diff --git a/src/components/views/auth/InteractiveAuthEntryComponents.tsx b/src/components/views/auth/InteractiveAuthEntryComponents.tsx
index a60aca3794..8431bfc01c 100644
--- a/src/components/views/auth/InteractiveAuthEntryComponents.tsx
+++ b/src/components/views/auth/InteractiveAuthEntryComponents.tsx
@@ -556,8 +556,8 @@ export class MsisdnAuthEntry extends React.Component<IMsisdnAuthEntryProps, IMsi
     public static LOGIN_TYPE = AuthType.Msisdn;
 
     private submitUrl?: string;
-    private sid: string;
-    private msisdn: string;
+    private sid?: string;
+    private msisdn?: string;
 
     public constructor(props: IMsisdnAuthEntryProps) {
         super(props);
@@ -615,8 +615,8 @@ export class MsisdnAuthEntry extends React.Component<IMsisdnAuthEntryProps, IMsi
         });
 
         try {
-            let result;
-            if (this.submitUrl) {
+            let result: { success: boolean };
+            if (this.submitUrl && this.sid) {
                 result = await this.props.matrixClient.submitMsisdnTokenOtherUrl(
                     this.submitUrl,
                     this.sid,
diff --git a/src/components/views/dialogs/ReportEventDialog.tsx b/src/components/views/dialogs/ReportEventDialog.tsx
index 8ce08208c0..43ea543ac9 100644
--- a/src/components/views/dialogs/ReportEventDialog.tsx
+++ b/src/components/views/dialogs/ReportEventDialog.tsx
@@ -19,7 +19,7 @@ import React, { ChangeEvent } from "react";
 import { MatrixEvent } from "matrix-js-sdk/src/models/event";
 import { logger } from "matrix-js-sdk/src/logger";
 
-import { _t } from "../../../languageHandler";
+import { _t, UserFriendlyError } from "../../../languageHandler";
 import { ensureDMExists } from "../../../createRoom";
 import { MatrixClientPeg } from "../../../MatrixClientPeg";
 import SdkConfig from "../../../SdkConfig";
@@ -245,6 +245,10 @@ export default class ReportEventDialog extends React.Component<IProps, IState> {
                 // Report to moderators through to the dedicated bot,
                 // as configured in the room's state events.
                 const dmRoomId = await ensureDMExists(client, this.moderation.moderationBotUserId);
+                if (!dmRoomId) {
+                    throw new UserFriendlyError("Unable to create room with moderation bot");
+                }
+
                 await client.sendEvent(dmRoomId, ABUSE_EVENT_TYPE, {
                     event_id: ev.getId(),
                     room_id: ev.getRoomId(),
diff --git a/src/components/views/dialogs/RoomSettingsDialog.tsx b/src/components/views/dialogs/RoomSettingsDialog.tsx
index 2c4a9745b5..55e49843b2 100644
--- a/src/components/views/dialogs/RoomSettingsDialog.tsx
+++ b/src/components/views/dialogs/RoomSettingsDialog.tsx
@@ -62,7 +62,7 @@ interface IState {
 }
 
 class RoomSettingsDialog extends React.Component<IProps, IState> {
-    private dispatcherRef: string;
+    private dispatcherRef?: string;
 
     public constructor(props: IProps) {
         super(props);
diff --git a/src/components/views/dialogs/RoomUpgradeDialog.tsx b/src/components/views/dialogs/RoomUpgradeDialog.tsx
index 9acf8b6ef8..7737f4fbc7 100644
--- a/src/components/views/dialogs/RoomUpgradeDialog.tsx
+++ b/src/components/views/dialogs/RoomUpgradeDialog.tsx
@@ -35,7 +35,7 @@ interface IState {
 }
 
 export default class RoomUpgradeDialog extends React.Component<IProps, IState> {
-    private targetVersion: string;
+    private targetVersion?: string;
 
     public state = {
         busy: true,
@@ -53,7 +53,7 @@ export default class RoomUpgradeDialog extends React.Component<IProps, IState> {
 
     private onUpgradeClick = (): void => {
         this.setState({ busy: true });
-        upgradeRoom(this.props.room, this.targetVersion, false, false)
+        upgradeRoom(this.props.room, this.targetVersion!, false, false)
             .then(() => {
                 this.props.onFinished(true);
             })
@@ -69,7 +69,7 @@ export default class RoomUpgradeDialog extends React.Component<IProps, IState> {
     };
 
     public render(): React.ReactNode {
-        let buttons;
+        let buttons: JSX.Element;
         if (this.state.busy) {
             buttons = <Spinner />;
         } else {
diff --git a/src/components/views/dialogs/ServerPickerDialog.tsx b/src/components/views/dialogs/ServerPickerDialog.tsx
index 8627e8b3d2..5a06db2da6 100644
--- a/src/components/views/dialogs/ServerPickerDialog.tsx
+++ b/src/components/views/dialogs/ServerPickerDialog.tsx
@@ -44,7 +44,7 @@ interface IState {
 export default class ServerPickerDialog extends React.PureComponent<IProps, IState> {
     private readonly defaultServer: ValidatedServerConfig;
     private readonly fieldRef = createRef<Field>();
-    private validatedConf: ValidatedServerConfig;
+    private validatedConf?: ValidatedServerConfig;
 
     public constructor(props: IProps) {
         super(props);
@@ -85,7 +85,7 @@ export default class ServerPickerDialog extends React.PureComponent<IProps, ISta
     // find their homeserver without demanding they use "https://matrix.org"
     private validate = withValidation<this, { error?: string }>({
         deriveData: async ({ value }): Promise<{ error?: string }> => {
-            let hsUrl = value.trim(); // trim to account for random whitespace
+            let hsUrl = (value ?? "").trim(); // trim to account for random whitespace
 
             // if the URL has no protocol, try validate it as a serverName via well-known
             if (!hsUrl.includes("://")) {
diff --git a/src/components/views/dialogs/SetEmailDialog.tsx b/src/components/views/dialogs/SetEmailDialog.tsx
index b5b148ea20..bec380e66a 100644
--- a/src/components/views/dialogs/SetEmailDialog.tsx
+++ b/src/components/views/dialogs/SetEmailDialog.tsx
@@ -45,7 +45,7 @@ interface IState {
  * On success, `onFinished(true)` is called.
  */
 export default class SetEmailDialog extends React.Component<IProps, IState> {
-    private addThreepid: AddThreepid;
+    private addThreepid?: AddThreepid;
 
     public constructor(props: IProps) {
         super(props);
@@ -109,7 +109,7 @@ export default class SetEmailDialog extends React.Component<IProps, IState> {
     };
 
     private verifyEmailAddress(): void {
-        this.addThreepid.checkEmailLinkClicked().then(
+        this.addThreepid?.checkEmailLinkClicked().then(
             () => {
                 this.props.onFinished(true);
             },
diff --git a/src/components/views/elements/AppTile.tsx b/src/components/views/elements/AppTile.tsx
index 5bc2678e70..2749836ee1 100644
--- a/src/components/views/elements/AppTile.tsx
+++ b/src/components/views/elements/AppTile.tsx
@@ -121,11 +121,11 @@ export default class AppTile extends React.Component<IProps, IState> {
     };
 
     private contextMenuButton = createRef<any>();
-    private iframe: HTMLIFrameElement; // ref to the iframe (callback style)
-    private allowedWidgetsWatchRef: string;
+    private iframe?: HTMLIFrameElement; // ref to the iframe (callback style)
+    private allowedWidgetsWatchRef?: string;
     private persistKey: string;
     private sgWidget: StopGapWidget | null;
-    private dispatcherRef: string;
+    private dispatcherRef?: string;
     private unmounted: boolean;
 
     public constructor(props: IProps) {
@@ -305,7 +305,7 @@ export default class AppTile extends React.Component<IProps, IState> {
             this.context.off(RoomEvent.MyMembership, this.onMyMembership);
         }
 
-        SettingsStore.unwatchSetting(this.allowedWidgetsWatchRef);
+        if (this.allowedWidgetsWatchRef) SettingsStore.unwatchSetting(this.allowedWidgetsWatchRef);
         OwnProfileStore.instance.removeListener(UPDATE_EVENT, this.onUserReady);
     }
 
@@ -344,7 +344,7 @@ export default class AppTile extends React.Component<IProps, IState> {
 
     private startMessaging(): void {
         try {
-            this.sgWidget?.startMessaging(this.iframe);
+            this.sgWidget?.startMessaging(this.iframe!);
         } catch (e) {
             logger.error("Failed to start widget", e);
         }
diff --git a/src/components/views/elements/DesktopCapturerSourcePicker.tsx b/src/components/views/elements/DesktopCapturerSourcePicker.tsx
index 20bbc729ad..fd9e019ee6 100644
--- a/src/components/views/elements/DesktopCapturerSourcePicker.tsx
+++ b/src/components/views/elements/DesktopCapturerSourcePicker.tsx
@@ -88,7 +88,7 @@ export interface PickerIProps {
 type TabId = "screen" | "window";
 
 export default class DesktopCapturerSourcePicker extends React.Component<PickerIProps, PickerIState> {
-    public interval: number;
+    public interval?: number;
 
     public constructor(props: PickerIProps) {
         super(props);
diff --git a/src/components/views/elements/PersistedElement.tsx b/src/components/views/elements/PersistedElement.tsx
index dd2c41b249..b1d53247db 100644
--- a/src/components/views/elements/PersistedElement.tsx
+++ b/src/components/views/elements/PersistedElement.tsx
@@ -75,8 +75,8 @@ interface IProps {
 export default class PersistedElement extends React.Component<IProps> {
     private resizeObserver: ResizeObserver;
     private dispatcherRef: string;
-    private childContainer: HTMLDivElement;
-    private child: HTMLDivElement;
+    private childContainer?: HTMLDivElement;
+    private child?: HTMLDivElement;
 
     public constructor(props: IProps) {
         super(props);
@@ -172,12 +172,12 @@ export default class PersistedElement extends React.Component<IProps> {
         ReactDOM.render(content, getOrCreateContainer("mx_persistedElement_" + this.props.persistKey));
     }
 
-    private updateChildVisibility(child: HTMLDivElement, visible: boolean): void {
+    private updateChildVisibility(child?: HTMLDivElement, visible = false): void {
         if (!child) return;
         child.style.display = visible ? "block" : "none";
     }
 
-    private updateChildPosition(child: HTMLDivElement, parent: HTMLDivElement): void {
+    private updateChildPosition(child?: HTMLDivElement, parent?: HTMLDivElement): void {
         if (!child || !parent) return;
 
         const parentRect = parent.getBoundingClientRect();
diff --git a/src/components/views/messages/IMediaBody.ts b/src/components/views/messages/IMediaBody.ts
index 27b5f24275..b578edbbef 100644
--- a/src/components/views/messages/IMediaBody.ts
+++ b/src/components/views/messages/IMediaBody.ts
@@ -17,5 +17,5 @@ limitations under the License.
 import { MediaEventHelper } from "../../../utils/MediaEventHelper";
 
 export interface IMediaBody {
-    getMediaHelper(): MediaEventHelper;
+    getMediaHelper(): MediaEventHelper | undefined;
 }
diff --git a/src/components/views/messages/LegacyCallEvent.tsx b/src/components/views/messages/LegacyCallEvent.tsx
index a8ba902e61..6d7bc3db8f 100644
--- a/src/components/views/messages/LegacyCallEvent.tsx
+++ b/src/components/views/messages/LegacyCallEvent.tsx
@@ -48,7 +48,7 @@ interface IState {
 
 export default class LegacyCallEvent extends React.PureComponent<IProps, IState> {
     private wrapperElement = createRef<HTMLDivElement>();
-    private resizeObserver: ResizeObserver;
+    private resizeObserver?: ResizeObserver;
 
     public constructor(props: IProps) {
         super(props);
@@ -75,7 +75,7 @@ export default class LegacyCallEvent extends React.PureComponent<IProps, IState>
         this.props.callEventGrouper.removeListener(LegacyCallEventGrouperEvent.SilencedChanged, this.onSilencedChanged);
         this.props.callEventGrouper.removeListener(LegacyCallEventGrouperEvent.LengthChanged, this.onLengthChanged);
 
-        this.resizeObserver.disconnect();
+        this.resizeObserver?.disconnect();
     }
 
     private onLengthChanged = (length: number): void => {
diff --git a/src/components/views/messages/MImageBody.tsx b/src/components/views/messages/MImageBody.tsx
index 27ccdd4228..e7c0964d16 100644
--- a/src/components/views/messages/MImageBody.tsx
+++ b/src/components/views/messages/MImageBody.tsx
@@ -69,7 +69,7 @@ export default class MImageBody extends React.Component<IBodyProps, IState> {
     private unmounted = true;
     private image = createRef<HTMLImageElement>();
     private timeout?: number;
-    private sizeWatcher: string;
+    private sizeWatcher?: string;
     private reconnectedListener: ClientEventHandlerMap[ClientEvent.Sync];
 
     public constructor(props: IBodyProps) {
@@ -367,7 +367,7 @@ export default class MImageBody extends React.Component<IBodyProps, IState> {
         this.unmounted = true;
         MatrixClientPeg.get().off(ClientEvent.Sync, this.reconnectedListener);
         this.clearBlurhashTimeout();
-        SettingsStore.unwatchSetting(this.sizeWatcher);
+        if (this.sizeWatcher) SettingsStore.unwatchSetting(this.sizeWatcher);
         if (this.state.isAnimated && this.state.thumbUrl) {
             URL.revokeObjectURL(this.state.thumbUrl);
         }
diff --git a/src/components/views/messages/MVideoBody.tsx b/src/components/views/messages/MVideoBody.tsx
index 6be311e868..5c2cd78fa8 100644
--- a/src/components/views/messages/MVideoBody.tsx
+++ b/src/components/views/messages/MVideoBody.tsx
@@ -45,7 +45,7 @@ export default class MVideoBody extends React.PureComponent<IBodyProps, IState>
     public context!: React.ContextType<typeof RoomContext>;
 
     private videoRef = React.createRef<HTMLVideoElement>();
-    private sizeWatcher: string;
+    private sizeWatcher?: string;
 
     public constructor(props: IBodyProps) {
         super(props);
@@ -187,7 +187,7 @@ export default class MVideoBody extends React.PureComponent<IBodyProps, IState>
     }
 
     public componentWillUnmount(): void {
-        SettingsStore.unwatchSetting(this.sizeWatcher);
+        if (this.sizeWatcher) SettingsStore.unwatchSetting(this.sizeWatcher);
     }
 
     private videoOnPlay = async (): Promise<void> => {
diff --git a/src/components/views/messages/MessageEvent.tsx b/src/components/views/messages/MessageEvent.tsx
index 65b7133b51..4fd84e31f1 100644
--- a/src/components/views/messages/MessageEvent.tsx
+++ b/src/components/views/messages/MessageEvent.tsx
@@ -82,7 +82,7 @@ const baseEvTypes = new Map<string, React.ComponentType<Partial<IBodyProps>>>([
 
 export default class MessageEvent extends React.Component<IProps> implements IMediaBody, IOperableEventTile {
     private body: React.RefObject<React.Component | IOperableEventTile> = createRef();
-    private mediaHelper: MediaEventHelper;
+    private mediaHelper?: MediaEventHelper;
     private bodyTypes = new Map<string, typeof React.Component>(baseBodyTypes.entries());
     private evTypes = new Map<string, React.ComponentType<Partial<IBodyProps>>>(baseEvTypes.entries());
 
@@ -133,7 +133,7 @@ export default class MessageEvent extends React.Component<IProps> implements IMe
         return (this.body.current as IOperableEventTile)?.getEventTileOps?.() || null;
     };
 
-    public getMediaHelper(): MediaEventHelper {
+    public getMediaHelper(): MediaEventHelper | undefined {
         return this.mediaHelper;
     }
 
diff --git a/src/components/views/rooms/AppsDrawer.tsx b/src/components/views/rooms/AppsDrawer.tsx
index e869c9ee5b..90fb65a3c9 100644
--- a/src/components/views/rooms/AppsDrawer.tsx
+++ b/src/components/views/rooms/AppsDrawer.tsx
@@ -57,9 +57,9 @@ interface IState {
 
 export default class AppsDrawer extends React.Component<IProps, IState> {
     private unmounted = false;
-    private resizeContainer: HTMLDivElement;
+    private resizeContainer?: HTMLDivElement;
     private resizer: Resizer;
-    private dispatcherRef: string;
+    private dispatcherRef?: string;
     public static defaultProps: Partial<IProps> = {
         showApps: true,
     };
@@ -113,11 +113,11 @@ export default class AppsDrawer extends React.Component<IProps, IState> {
         };
         const collapseConfig = {
             onResizeStart: () => {
-                this.resizeContainer.classList.add("mx_AppsDrawer_resizing");
+                this.resizeContainer?.classList.add("mx_AppsDrawer_resizing");
                 this.setState({ resizingHorizontal: true });
             },
             onResizeStop: () => {
-                this.resizeContainer.classList.remove("mx_AppsDrawer_resizing");
+                this.resizeContainer?.classList.remove("mx_AppsDrawer_resizing");
                 WidgetLayoutStore.instance.setResizerDistributions(
                     this.props.room,
                     Container.Top,
diff --git a/src/components/views/rooms/Autocomplete.tsx b/src/components/views/rooms/Autocomplete.tsx
index b8f643eebb..667f93afa1 100644
--- a/src/components/views/rooms/Autocomplete.tsx
+++ b/src/components/views/rooms/Autocomplete.tsx
@@ -133,9 +133,9 @@ export default class Autocomplete extends React.PureComponent<IProps, IState> {
         });
     }
 
-    private processQuery(query: string, selection: ISelectionRange): Promise<void> {
+    private async processQuery(query: string, selection: ISelectionRange): Promise<void> {
         return this.autocompleter
-            .getCompletions(query, selection, this.state.forceComplete, MAX_PROVIDER_MATCHES)
+            ?.getCompletions(query, selection, this.state.forceComplete, MAX_PROVIDER_MATCHES)
             .then((completions) => {
                 // Only ever process the completions for the most recent query being processed
                 if (query !== this.queryRequested) {
diff --git a/src/components/views/rooms/EditMessageComposer.tsx b/src/components/views/rooms/EditMessageComposer.tsx
index c1fdecdd47..9b581565cc 100644
--- a/src/components/views/rooms/EditMessageComposer.tsx
+++ b/src/components/views/rooms/EditMessageComposer.tsx
@@ -129,7 +129,7 @@ class EditMessageComposer extends React.Component<IEditMessageComposerProps, ISt
     private readonly editorRef = createRef<BasicMessageComposer>();
     private readonly dispatcherRef: string;
     private readonly replyToEvent?: MatrixEvent;
-    private model: EditorModel;
+    private model!: EditorModel;
 
     public constructor(props: IEditMessageComposerProps, context: React.ContextType<typeof RoomContext>) {
         super(props);
diff --git a/src/components/views/rooms/MemberTile.tsx b/src/components/views/rooms/MemberTile.tsx
index 7ff46c922f..f8f891a486 100644
--- a/src/components/views/rooms/MemberTile.tsx
+++ b/src/components/views/rooms/MemberTile.tsx
@@ -46,8 +46,8 @@ interface IState {
 }
 
 export default class MemberTile extends React.Component<IProps, IState> {
-    private userLastModifiedTime: number;
-    private memberLastModifiedTime: number;
+    private userLastModifiedTime?: number;
+    private memberLastModifiedTime?: number;
 
     public static defaultProps = {
         showPresence: true,
diff --git a/src/components/views/rooms/RoomList.tsx b/src/components/views/rooms/RoomList.tsx
index 921c1e2467..06396de03c 100644
--- a/src/components/views/rooms/RoomList.tsx
+++ b/src/components/views/rooms/RoomList.tsx
@@ -443,7 +443,7 @@ const TAG_AESTHETICS: TagAestheticsMap = {
 export default class RoomList extends React.PureComponent<IProps, IState> {
     private dispatcherRef?: string;
     private treeRef = createRef<HTMLDivElement>();
-    private favouriteMessageWatcher: string;
+    private favouriteMessageWatcher?: string;
 
     public static contextType = MatrixClientContext;
     public context!: React.ContextType<typeof MatrixClientContext>;
@@ -476,7 +476,7 @@ export default class RoomList extends React.PureComponent<IProps, IState> {
     public componentWillUnmount(): void {
         SpaceStore.instance.off(UPDATE_SUGGESTED_ROOMS, this.updateSuggestedRooms);
         RoomListStore.instance.off(LISTS_UPDATE_EVENT, this.updateLists);
-        SettingsStore.unwatchSetting(this.favouriteMessageWatcher);
+        if (this.favouriteMessageWatcher) SettingsStore.unwatchSetting(this.favouriteMessageWatcher);
         if (this.dispatcherRef) defaultDispatcher.unregister(this.dispatcherRef);
         SdkContextClass.instance.roomViewStore.off(UPDATE_EVENT, this.onRoomViewStoreUpdate);
     }
diff --git a/src/components/views/rooms/RoomPreviewBar.tsx b/src/components/views/rooms/RoomPreviewBar.tsx
index 32fb134953..77b1603a23 100644
--- a/src/components/views/rooms/RoomPreviewBar.tsx
+++ b/src/components/views/rooms/RoomPreviewBar.tsx
@@ -215,8 +215,10 @@ export default class RoomPreviewBar extends React.Component<IProps, IState> {
         if (!myMember) {
             return {};
         }
-        const kickerMember = this.props.room?.currentState.getMember(myMember.events.member.getSender());
-        const memberName = kickerMember?.name ?? myMember.events.member?.getSender();
+
+        const kickerUserId = myMember.events.member?.getSender();
+        const kickerMember = kickerUserId ? this.props.room?.currentState.getMember(kickerUserId) : undefined;
+        const memberName = kickerMember?.name ?? kickerUserId;
         const reason = myMember.events.member?.getContent().reason;
         return { memberName, reason };
     }
@@ -559,7 +561,7 @@ export default class RoomPreviewBar extends React.Component<IProps, IState> {
                         "%(errcode)s was returned while trying to access the room or space. " +
                             "If you think you're seeing this message in error, please " +
                             "<issueLink>submit a bug report</issueLink>.",
-                        { errcode: this.props.error.errcode },
+                        { errcode: String(this.props.error?.errcode) },
                         {
                             issueLink: (label) => (
                                 <a
diff --git a/src/components/views/rooms/RoomSublist.tsx b/src/components/views/rooms/RoomSublist.tsx
index 5aa20058d8..c4b3efa3e6 100644
--- a/src/components/views/rooms/RoomSublist.tsx
+++ b/src/components/views/rooms/RoomSublist.tsx
@@ -110,7 +110,7 @@ export default class RoomSublist extends React.Component<IProps, IState> {
     private headerButton = createRef<HTMLDivElement>();
     private sublistRef = createRef<HTMLDivElement>();
     private tilesRef = createRef<HTMLDivElement>();
-    private dispatcherRef: string;
+    private dispatcherRef?: string;
     private layout: ListLayout;
     private heightAtStart: number;
     private notificationState: ListNotificationState;
@@ -257,7 +257,7 @@ export default class RoomSublist extends React.Component<IProps, IState> {
     }
 
     public componentWillUnmount(): void {
-        defaultDispatcher.unregister(this.dispatcherRef);
+        if (this.dispatcherRef) defaultDispatcher.unregister(this.dispatcherRef);
         RoomListStore.instance.off(LISTS_UPDATE_EVENT, this.onListsUpdated);
         RoomListStore.instance.off(LISTS_LOADING_EVENT, this.onListsLoading);
         this.tilesRef.current?.removeEventListener("scroll", this.onScrollPrevent);
diff --git a/src/components/views/rooms/Stickerpicker.tsx b/src/components/views/rooms/Stickerpicker.tsx
index dc6c4fd34d..1e14164620 100644
--- a/src/components/views/rooms/Stickerpicker.tsx
+++ b/src/components/views/rooms/Stickerpicker.tsx
@@ -23,7 +23,7 @@ import AppTile from "../elements/AppTile";
 import { MatrixClientPeg } from "../../../MatrixClientPeg";
 import dis from "../../../dispatcher/dispatcher";
 import AccessibleButton from "../elements/AccessibleButton";
-import WidgetUtils, { IWidgetEvent } from "../../../utils/WidgetUtils";
+import WidgetUtils, { UserWidget } from "../../../utils/WidgetUtils";
 import PersistedElement from "../elements/PersistedElement";
 import { IntegrationManagers } from "../../../integrations/IntegrationManagers";
 import ContextMenu, { ChevronFace } from "../../structures/ContextMenu";
@@ -53,7 +53,7 @@ interface IProps {
 
 interface IState {
     imError: string | null;
-    stickerpickerWidget: IWidgetEvent | null;
+    stickerpickerWidget: UserWidget | null;
     widgetId: string | null;
 }
 
@@ -62,7 +62,7 @@ export default class Stickerpicker extends React.PureComponent<IProps, IState> {
         threadId: null,
     };
 
-    public static currentWidget?: IWidgetEvent;
+    public static currentWidget?: UserWidget;
 
     private dispatcherRef?: string;
 
@@ -252,14 +252,14 @@ export default class Stickerpicker extends React.PureComponent<IProps, IState> {
         // Render content from multiple stickerpack sources, each within their
         // own iframe, within the stickerpicker UI element.
         const stickerpickerWidget = this.state.stickerpickerWidget;
-        let stickersContent;
+        let stickersContent: JSX.Element | undefined;
 
         // Use a separate ReactDOM tree to render the AppTile separately so that it persists and does
         // not unmount when we (a) close the sticker picker (b) switch rooms. It's properties are still
         // updated.
 
         // Load stickerpack content
-        if (stickerpickerWidget && stickerpickerWidget.content && stickerpickerWidget.content.url) {
+        if (!!stickerpickerWidget?.content?.url) {
             // Set default name
             stickerpickerWidget.content.name = stickerpickerWidget.content.name || _t("Stickerpack");
 
diff --git a/src/components/views/settings/ChangePassword.tsx b/src/components/views/settings/ChangePassword.tsx
index 0a32646878..69e30948b4 100644
--- a/src/components/views/settings/ChangePassword.tsx
+++ b/src/components/views/settings/ChangePassword.tsx
@@ -69,9 +69,9 @@ interface IState {
 }
 
 export default class ChangePassword extends React.Component<IProps, IState> {
-    private [FIELD_OLD_PASSWORD]: Field | null;
-    private [FIELD_NEW_PASSWORD]: Field | null;
-    private [FIELD_NEW_PASSWORD_CONFIRM]: Field | null;
+    private [FIELD_OLD_PASSWORD]: Field | null = null;
+    private [FIELD_NEW_PASSWORD]: Field | null = null;
+    private [FIELD_NEW_PASSWORD_CONFIRM]: Field | null = null;
 
     public static defaultProps: Partial<IProps> = {
         onFinished() {},
diff --git a/src/components/views/settings/IntegrationManager.tsx b/src/components/views/settings/IntegrationManager.tsx
index ee69c5cd92..16e9f1ed56 100644
--- a/src/components/views/settings/IntegrationManager.tsx
+++ b/src/components/views/settings/IntegrationManager.tsx
@@ -43,7 +43,7 @@ interface IState {
 }
 
 export default class IntegrationManager extends React.Component<IProps, IState> {
-    private dispatcherRef: string;
+    private dispatcherRef?: string;
 
     public static defaultProps: Partial<IProps> = {
         connected: true,
@@ -60,7 +60,7 @@ export default class IntegrationManager extends React.Component<IProps, IState>
     }
 
     public componentWillUnmount(): void {
-        dis.unregister(this.dispatcherRef);
+        if (this.dispatcherRef) dis.unregister(this.dispatcherRef);
         document.removeEventListener("keydown", this.onKeyDown);
     }
 
diff --git a/src/components/views/settings/SetIdServer.tsx b/src/components/views/settings/SetIdServer.tsx
index 6e1e6b8e35..8cc3444c3e 100644
--- a/src/components/views/settings/SetIdServer.tsx
+++ b/src/components/views/settings/SetIdServer.tsx
@@ -81,7 +81,7 @@ interface IState {
 }
 
 export default class SetIdServer extends React.Component<IProps, IState> {
-    private dispatcherRef: string;
+    private dispatcherRef?: string;
 
     public constructor(props: IProps) {
         super(props);
@@ -108,7 +108,7 @@ export default class SetIdServer extends React.Component<IProps, IState> {
     }
 
     public componentWillUnmount(): void {
-        dis.unregister(this.dispatcherRef);
+        if (this.dispatcherRef) dis.unregister(this.dispatcherRef);
     }
 
     private onAction = (payload: ActionPayload): void => {
diff --git a/src/customisations/Media.ts b/src/customisations/Media.ts
index e9cade175f..879e7169c4 100644
--- a/src/customisations/Media.ts
+++ b/src/customisations/Media.ts
@@ -20,6 +20,7 @@ import { Optional } from "matrix-events-sdk";
 
 import { MatrixClientPeg } from "../MatrixClientPeg";
 import { IMediaEventContent, IPreparedMedia, prepEventContentAsMedia } from "./models/IMediaEventContent";
+import { UserFriendlyError } from "../languageHandler";
 
 // Populate this class with the details of your customisations when copying it.
 
@@ -141,7 +142,11 @@ export class Media {
      * @returns {Promise<Response>} Resolves to the server's response for chaining.
      */
     public downloadSource(): Promise<Response> {
-        return fetch(this.srcHttp);
+        const src = this.srcHttp;
+        if (!src) {
+            throw new UserFriendlyError("Failed to download source media, no source url was found");
+        }
+        return fetch(src);
     }
 }
 
diff --git a/src/i18n/strings/en_EN.json b/src/i18n/strings/en_EN.json
index 277da44a9c..9a6b076cfd 100644
--- a/src/i18n/strings/en_EN.json
+++ b/src/i18n/strings/en_EN.json
@@ -1130,6 +1130,7 @@
     "You can use <code>/help</code> to list available commands. Did you mean to send this as a message?": "You can use <code>/help</code> to list available commands. Did you mean to send this as a message?",
     "Hint: Begin your message with <code>//</code> to start it with a slash.": "Hint: Begin your message with <code>//</code> to start it with a slash.",
     "Send as message": "Send as message",
+    "Failed to download source media, no source url was found": "Failed to download source media, no source url was found",
     "Audio devices": "Audio devices",
     "Mute microphone": "Mute microphone",
     "Unmute microphone": "Unmute microphone",
@@ -2975,6 +2976,7 @@
     "Just a heads up, if you don't add an email and forget your password, you could <b>permanently lose access to your account</b>.": "Just a heads up, if you don't add an email and forget your password, you could <b>permanently lose access to your account</b>.",
     "Email (optional)": "Email (optional)",
     "Please fill why you're reporting.": "Please fill why you're reporting.",
+    "Unable to create room with moderation bot": "Unable to create room with moderation bot",
     "Ignore user": "Ignore user",
     "Check if you want to hide all current and future messages from this user.": "Check if you want to hide all current and future messages from this user.",
     "What this user is writing is wrong.\nThis will be reported to the room moderators.": "What this user is writing is wrong.\nThis will be reported to the room moderators.",
diff --git a/src/stores/RoomViewStore.tsx b/src/stores/RoomViewStore.tsx
index 7713e3f005..2f8c80023f 100644
--- a/src/stores/RoomViewStore.tsx
+++ b/src/stores/RoomViewStore.tsx
@@ -150,8 +150,8 @@ export class RoomViewStore extends EventEmitter {
     // another RVS via INITIAL_STATE as they share the same underlying object. Mostly relevant for tests.
     private state = utils.deepCopy(INITIAL_STATE);
 
-    private dis: MatrixDispatcher;
-    private dispatchToken: string;
+    private dis?: MatrixDispatcher;
+    private dispatchToken?: string;
 
     public constructor(dis: MatrixDispatcher, private readonly stores: SdkContextClass) {
         super();
@@ -217,7 +217,7 @@ export class RoomViewStore extends EventEmitter {
 
             // Fired so we can reduce dependency on event emitters to this store, which is relatively
             // central to the application and can easily cause import cycles.
-            this.dis.dispatch<ActiveRoomChangedPayload>({
+            this.dis?.dispatch<ActiveRoomChangedPayload>({
                 action: Action.ActiveRoomChanged,
                 oldRoomId: lastRoomId,
                 newRoomId: this.state.roomId,
@@ -343,7 +343,7 @@ export class RoomViewStore extends EventEmitter {
                     // can happen when performing a search across all rooms. Persist the data from this event for both
                     // room and search timeline rendering types, search will get auto-closed by RoomView at this time.
                     if (payload.event && payload.event.getRoomId() !== this.state.roomId) {
-                        this.dis.dispatch<ViewRoomPayload>({
+                        this.dis?.dispatch<ViewRoomPayload>({
                             action: Action.ViewRoom,
                             room_id: payload.event.getRoomId(),
                             replyingToEvent: payload.event,
@@ -414,7 +414,7 @@ export class RoomViewStore extends EventEmitter {
                     return;
                 }
                 // Re-fire the payload: we won't re-process it because the prev room ID == payload room ID now
-                this.dis.dispatch({
+                this.dis?.dispatch({
                     ...payload,
                 });
                 return;
@@ -455,7 +455,7 @@ export class RoomViewStore extends EventEmitter {
             this.setState(newState);
 
             if (payload.auto_join) {
-                this.dis.dispatch<JoinRoomPayload>({
+                this.dis?.dispatch<JoinRoomPayload>({
                     ...payload,
                     action: Action.JoinRoom,
                     roomId: payload.room_id,
@@ -493,7 +493,7 @@ export class RoomViewStore extends EventEmitter {
                     roomId = result.room_id;
                 } catch (err) {
                     logger.error("RVS failed to get room id for alias: ", err);
-                    this.dis.dispatch<ViewRoomErrorPayload>({
+                    this.dis?.dispatch<ViewRoomErrorPayload>({
                         action: Action.ViewRoomError,
                         room_id: null,
                         room_alias: payload.room_alias,
@@ -504,7 +504,7 @@ export class RoomViewStore extends EventEmitter {
             }
 
             // Re-fire the payload with the newly found room_id
-            this.dis.dispatch({
+            this.dis?.dispatch({
                 ...payload,
                 room_id: roomId,
             });
@@ -553,13 +553,13 @@ export class RoomViewStore extends EventEmitter {
             // We do *not* clear the 'joining' flag because the Room object and/or our 'joined' member event may not
             // have come down the sync stream yet, and that's the point at which we'd consider the user joined to the
             // room.
-            this.dis.dispatch<JoinRoomReadyPayload>({
+            this.dis?.dispatch<JoinRoomReadyPayload>({
                 action: Action.JoinRoomReady,
                 roomId: roomId!,
                 metricsTrigger: payload.metricsTrigger,
             });
         } catch (err) {
-            this.dis.dispatch({
+            this.dis?.dispatch({
                 action: Action.JoinRoomError,
                 roomId,
                 err,
@@ -648,7 +648,7 @@ export class RoomViewStore extends EventEmitter {
      */
     public resetDispatcher(dis: MatrixDispatcher): void {
         if (this.dispatchToken) {
-            this.dis.unregister(this.dispatchToken);
+            this.dis?.unregister(this.dispatchToken);
         }
         this.dis = dis;
         if (dis) {
diff --git a/src/stores/SetupEncryptionStore.ts b/src/stores/SetupEncryptionStore.ts
index 353d361795..9e7505d495 100644
--- a/src/stores/SetupEncryptionStore.ts
+++ b/src/stores/SetupEncryptionStore.ts
@@ -44,7 +44,7 @@ export enum Phase {
 }
 
 export class SetupEncryptionStore extends EventEmitter {
-    private started: boolean;
+    private started?: boolean;
     public phase: Phase;
     public verificationRequest: VerificationRequest | null = null;
     public backupInfo: IKeyBackupInfo | null = null;
@@ -52,7 +52,7 @@ export class SetupEncryptionStore extends EventEmitter {
     public keyId: string | null = null;
     // Descriptor of the key that the secrets we want are encrypted with
     public keyInfo: ISecretStorageKeyInfo | null = null;
-    public hasDevicesToVerifyAgainst: boolean;
+    public hasDevicesToVerifyAgainst?: boolean;
 
     public static sharedInstance(): SetupEncryptionStore {
         if (!window.mxSetupEncryptionStore) window.mxSetupEncryptionStore = new SetupEncryptionStore();
diff --git a/src/stores/TypingStore.ts b/src/stores/TypingStore.ts
index f76f4c0949..8346d12a75 100644
--- a/src/stores/TypingStore.ts
+++ b/src/stores/TypingStore.ts
@@ -32,7 +32,7 @@ export default class TypingStore {
             userTimer: Timer;
             serverTimer: Timer;
         };
-    };
+    } = {};
 
     public constructor(private readonly context: SdkContextClass) {
         this.reset();
@@ -68,7 +68,7 @@ export default class TypingStore {
         if (threadId) return;
 
         let currentTyping = this.typingStates[roomId];
-        if ((!isTyping && !currentTyping) || (currentTyping && currentTyping.isTyping === isTyping)) {
+        if ((!isTyping && !currentTyping) || currentTyping?.isTyping === isTyping) {
             // No change in state, so don't do anything. We'll let the timer run its course.
             return;
         }
diff --git a/src/stores/widgets/StopGapWidget.ts b/src/stores/widgets/StopGapWidget.ts
index da5f956bbe..90f1d32ff1 100644
--- a/src/stores/widgets/StopGapWidget.ts
+++ b/src/stores/widgets/StopGapWidget.ts
@@ -157,9 +157,9 @@ export class ElementWidget extends Widget {
 
 export class StopGapWidget extends EventEmitter {
     private client: MatrixClient;
-    private messaging: ClientWidgetApi | null;
+    private messaging: ClientWidgetApi | null = null;
     private mockWidget: ElementWidget;
-    private scalarToken: string;
+    private scalarToken?: string;
     private roomId?: string;
     private kind: WidgetKind;
     private readonly virtual: boolean;
diff --git a/src/utils/DMRoomMap.ts b/src/utils/DMRoomMap.ts
index 37c0f873bc..5aab198e62 100644
--- a/src/utils/DMRoomMap.ts
+++ b/src/utils/DMRoomMap.ts
@@ -39,7 +39,7 @@ export default class DMRoomMap {
     private roomToUser: { [key: string]: string } | null = null;
     private userToRooms: { [key: string]: string[] } | null = null;
     private hasSentOutPatchDirectAccountDataPatch: boolean;
-    private mDirectEvent: { [key: string]: string[] };
+    private mDirectEvent!: { [key: string]: string[] };
 
     public constructor(private readonly matrixClient: MatrixClient) {
         // see onAccountData
diff --git a/src/utils/WidgetUtils.ts b/src/utils/WidgetUtils.ts
index 00d10c9d3c..2c4f01b011 100644
--- a/src/utils/WidgetUtils.ts
+++ b/src/utils/WidgetUtils.ts
@@ -47,7 +47,11 @@ export interface IWidgetEvent {
     sender: string;
     // eslint-disable-next-line camelcase
     state_key: string;
-    content: Partial<IApp>;
+    content: IApp;
+}
+
+export interface UserWidget extends Omit<IWidgetEvent, "content"> {
+    content: IWidget & Partial<IApp>;
 }
 
 export default class WidgetUtils {
@@ -254,6 +258,7 @@ export default class WidgetUtils {
         const userId = client.getSafeUserId();
 
         const content = {
+            id: widgetId,
             type: widgetType.preferred,
             url: widgetUrl,
             name: widgetName,
@@ -354,7 +359,7 @@ export default class WidgetUtils {
      * Get user specific widgets (not linked to a specific room)
      * @return {object} Event content object containing current / active user widgets
      */
-    public static getUserWidgets(): Record<string, IWidgetEvent> {
+    public static getUserWidgets(): Record<string, UserWidget> {
         const client = MatrixClientPeg.get();
         if (!client) {
             throw new Error("User not logged in");
@@ -370,7 +375,7 @@ export default class WidgetUtils {
      * Get user specific widgets (not linked to a specific room) as an array
      * @return {[object]} Array containing current / active user widgets
      */
-    public static getUserWidgetsArray(): IWidgetEvent[] {
+    public static getUserWidgetsArray(): UserWidget[] {
         return Object.values(WidgetUtils.getUserWidgets());
     }
 
@@ -378,18 +383,18 @@ export default class WidgetUtils {
      * Get active stickerpicker widgets (stickerpickers are user widgets by nature)
      * @return {[object]} Array containing current / active stickerpicker widgets
      */
-    public static getStickerpickerWidgets(): IWidgetEvent[] {
+    public static getStickerpickerWidgets(): UserWidget[] {
         const widgets = WidgetUtils.getUserWidgetsArray();
-        return widgets.filter((widget) => widget.content && widget.content.type === "m.stickerpicker");
+        return widgets.filter((widget) => widget.content?.type === "m.stickerpicker");
     }
 
     /**
      * Get all integration manager widgets for this user.
      * @returns {Object[]} An array of integration manager user widgets.
      */
-    public static getIntegrationManagerWidgets(): IWidgetEvent[] {
+    public static getIntegrationManagerWidgets(): UserWidget[] {
         const widgets = WidgetUtils.getUserWidgetsArray();
-        return widgets.filter((w) => w.content && w.content.type === "m.integration_manager");
+        return widgets.filter((w) => w.content?.type === "m.integration_manager");
     }
 
     public static getRoomWidgetsOfType(room: Room, type: WidgetType): MatrixEvent[] {
diff --git a/src/voice-broadcast/audio/VoiceBroadcastRecorder.ts b/src/voice-broadcast/audio/VoiceBroadcastRecorder.ts
index a05ce956c1..ab4daae830 100644
--- a/src/voice-broadcast/audio/VoiceBroadcastRecorder.ts
+++ b/src/voice-broadcast/audio/VoiceBroadcastRecorder.ts
@@ -126,7 +126,7 @@ export class VoiceBroadcastRecorder
             return;
         }
 
-        this.setCurrentChunkLength(this.voiceRecording.recorderSeconds - this.previousChunkEndTimePosition);
+        this.setCurrentChunkLength(this.voiceRecording.recorderSeconds! - this.previousChunkEndTimePosition);
         this.handleData(dataArray);
     };
 
@@ -154,7 +154,7 @@ export class VoiceBroadcastRecorder
             return null;
         }
 
-        const currentRecorderTime = this.voiceRecording.recorderSeconds;
+        const currentRecorderTime = this.voiceRecording.recorderSeconds!;
         const payload: ChunkRecordedPayload = {
             buffer: concat(this.opusHead!, this.opusTags!, this.chunkBuffer),
             length: this.getCurrentChunkLength(),
diff --git a/test/settings/watchers/ThemeWatcher-test.tsx b/test/settings/watchers/ThemeWatcher-test.tsx
index 48981a4038..3af6b42430 100644
--- a/test/settings/watchers/ThemeWatcher-test.tsx
+++ b/test/settings/watchers/ThemeWatcher-test.tsx
@@ -21,8 +21,8 @@ import { SettingLevel } from "../../../src/settings/SettingLevel";
 function makeMatchMedia(values: any) {
     class FakeMediaQueryList {
         matches: false;
-        media: null;
-        onchange: null;
+        media?: null;
+        onchange?: null;
         addListener() {}
         removeListener() {}
         addEventListener() {}