diff --git a/src/app/hooks/useCallSpeakers.ts b/src/app/hooks/useCallSpeakers.ts
index 836621bf6..3c5a3d255 100644
--- a/src/app/hooks/useCallSpeakers.ts
+++ b/src/app/hooks/useCallSpeakers.ts
@@ -1,5 +1,6 @@
 import { useEffect, useState } from 'react';
 import { CallEmbed } from '../plugins/call';
+import { getCallDocument } from '../plugins/call/utils';
 import { isUserId } from '../utils/matrix';
 import { nextSpeakerSet } from '../utils/speakerSet';
 import { useCallMembers, useCallSession } from './useCall';
@@ -38,8 +39,7 @@ export const useCallSpeakers = (callEmbed: CallEmbed): Set<string> => {
       return undefined;
     }
 
-    const getDoc = (): Document | undefined =>
-      callEmbed.iframe.contentDocument ?? callEmbed.iframe.contentWindow?.document ?? undefined;
+    const getDoc = (): Document | undefined => getCallDocument(callEmbed.iframe);
 
     let tileObserver: MutationObserver | undefined;
 
@@ -163,8 +163,7 @@ export const useRemoteAllMuted = (callEmbed: CallEmbed | undefined): boolean =>
   useEffect(() => {
     if (!callEmbed) return undefined;
 
-    const getDoc = (): Document | undefined =>
-      callEmbed.iframe.contentDocument ?? callEmbed.iframe.contentWindow?.document ?? undefined;
+    const getDoc = (): Document | undefined => getCallDocument(callEmbed.iframe);
 
     const localUserId = callEmbed.room.client?.getUserId() ?? '';
 
diff --git a/src/app/plugins/call/CallControl.ts b/src/app/plugins/call/CallControl.ts
index 9108c240d..db6554d4a 100644
--- a/src/app/plugins/call/CallControl.ts
+++ b/src/app/plugins/call/CallControl.ts
@@ -2,6 +2,7 @@ import { ClientWidgetApi } from 'matrix-widget-api';
 import { EventEmitter } from 'events';
 import { CallControlState } from './CallControlState';
 import { ElementMediaStateDetail, ElementMediaStatePayload, ElementWidgetActions } from './types';
+import { getCallDocument } from './utils';
 
 export enum CallControlEvent {
   StateUpdate = 'state_update',
@@ -62,7 +63,7 @@ export class CallControl extends EventEmitter implements CallControlState {
   private joined = false;
 
   private get document(): Document | undefined {
-    return this.iframe.contentDocument ?? this.iframe.contentWindow?.document;
+    return getCallDocument(this.iframe);
   }
 
   private get screenshareButton(): HTMLElement | undefined {
@@ -265,7 +266,7 @@ export class CallControl extends EventEmitter implements CallControlState {
   }
 
   private setSound(sound: boolean): void {
-    const callDocument = this.iframe.contentDocument ?? this.iframe.contentWindow?.document;
+    const callDocument = getCallDocument(this.iframe);
     if (callDocument) {
       callDocument.querySelectorAll('audio').forEach((el) => {
         const isScreenshareAudio = el.getAttribute('data-lk-source') === 'screen_share_audio';
@@ -277,7 +278,7 @@ export class CallControl extends EventEmitter implements CallControlState {
 
   private applyScreenshareAudioMuted(): void {
     if (!this.sound) return;
-    const callDocument = this.iframe.contentDocument ?? this.iframe.contentWindow?.document;
+    const callDocument = getCallDocument(this.iframe);
     if (callDocument) {
       callDocument
         .querySelectorAll<HTMLAudioElement>('audio[data-lk-source="screen_share_audio"]')
diff --git a/src/app/plugins/call/CallEmbed.ts b/src/app/plugins/call/CallEmbed.ts
index aec4d8efc..f6dd11e9a 100644
--- a/src/app/plugins/call/CallEmbed.ts
+++ b/src/app/plugins/call/CallEmbed.ts
@@ -28,6 +28,7 @@ import {
 import { CallControl } from './CallControl';
 import { CallControlState } from './CallControlState';
 import { verifyDenoiseAssets } from './denoiseSmokeCheck';
+import { getCallDocument } from './utils';
 
 // Maximum time to wait for the embedded Element Call iframe to progress from
 // initial load to a ready/joined state. If it hasn't by then, we assume the
@@ -326,7 +327,7 @@ export class CallEmbed {
   }
 
   get document(): Document | undefined {
-    return this.iframe.contentDocument ?? this.iframe.contentWindow?.document;
+    return getCallDocument(this.iframe);
   }
 
   public setTheme(theme: ElementCallThemeKind) {
diff --git a/src/app/plugins/call/utils.ts b/src/app/plugins/call/utils.ts
index 7841a5fa2..8ab35377a 100644
--- a/src/app/plugins/call/utils.ts
+++ b/src/app/plugins/call/utils.ts
@@ -116,3 +116,19 @@ export function getCallCapabilities(
 
   return capabilities;
 }
+
+/**
+ * The EC iframe's document, or undefined when it cannot be read. The widget is
+ * same-origin, but when its navigation fails (offline, blocked) the frame
+ * becomes a cross-origin error page and `contentWindow.document` THROWS a
+ * SecurityError — which surfaced as page errors (and a React "Should not
+ * already be working" cascade) from every DOM-driven call hook the moment the
+ * load watchdog fired. Treat "can't read" the same as "not loaded yet".
+ */
+export const getCallDocument = (iframe: HTMLIFrameElement): Document | undefined => {
+  try {
+    return iframe.contentDocument ?? iframe.contentWindow?.document ?? undefined;
+  } catch {
+    return undefined;
+  }
+};