2 files changed, 11 insertions, 6 deletions
diff --git a/src/client/views/nodes/DocumentView.tsx b/src/client/views/nodes/DocumentView.tsx
index 2ad8b8af0..8847c0c6a 100644
--- a/src/client/views/nodes/DocumentView.tsx
+++ b/src/client/views/nodes/DocumentView.tsx
@@ -239,7 +239,7 @@ export class DocumentViewInternal extends DocComponent<DocumentViewInternalProps
         return this.props.NativeDimScaling?.() || 1;
     }
     @computed get thumb() {
-        return ImageCast(this.layoutDoc['thumb-frozen'], ImageCast(this.layoutDoc.thumb))?.url.href.replace('.png', '_m.png');
+        return ImageCast(this.layoutDoc['thumb-frozen'], ImageCast(this.layoutDoc.thumb))?.url?.href.replace('.png', '_m.png');
     }
     @computed get hidden() {
         return this.props.styleProvider?.(this.rootDoc, this.props, StyleProp.Hidden);
@@ -1286,7 +1286,7 @@ export class DocumentViewInternal extends DocComponent<DocumentViewInternalProps
     @observable _: string = '';
     @computed get renderDoc() {
         TraceMobx();
-        const thumb = ImageCast(this.layoutDoc['thumb-frozen'], ImageCast(this.layoutDoc.thumb))?.url.href.replace('.png', '_m.png');
+        const thumb = ImageCast(this.layoutDoc['thumb-frozen'], ImageCast(this.layoutDoc.thumb))?.url?.href.replace('.png', '_m.png');
         const isButton = this.props.Document.type === DocumentType.FONTICON;
         if (!(this.props.Document instanceof Doc) || GetEffectiveAcl(this.props.Document[DataSym]) === AclPrivate || (this.hidden && !this.props.treeViewDoc)) return null;
         return (
diff --git a/src/client/views/nodes/WebBox.tsx b/src/client/views/nodes/WebBox.tsx
index dd14822af..ca9f363c1 100644
--- a/src/client/views/nodes/WebBox.tsx
+++ b/src/client/views/nodes/WebBox.tsx
@@ -134,25 +134,30 @@ export class WebBox extends ViewBoxAnnotatableComponent<ViewBoxAnnotatableProps
         }
     };
 
-    lockout = false;
     updateThumb = async () => {
         const imageBitmap = ImageCast(this.layoutDoc['thumb-frozen'])?.url.href;
         const scrollTop = NumCast(this.layoutDoc._scrollTop);
         const nativeWidth = NumCast(this.layoutDoc.nativeWidth);
         const nativeHeight = (nativeWidth * this.props.PanelHeight()) / this.props.PanelWidth();
-        if (!this.lockout && this._iframe && !imageBitmap && (scrollTop !== this.layoutDoc.thumbScrollTop || nativeWidth !== this.layoutDoc.thumbNativeWidth || nativeHeight !== this.layoutDoc.thumbNativeHeight)) {
+        if (
+            !this.rootDoc.thumbLockout &&
+            !this.props.dontRegisterView &&
+            this._iframe &&
+            !imageBitmap &&
+            (scrollTop !== this.layoutDoc.thumbScrollTop || nativeWidth !== this.layoutDoc.thumbNativeWidth || nativeHeight !== this.layoutDoc.thumbNativeHeight)
+        ) {
             var htmlString = this._iframe.contentDocument && new XMLSerializer().serializeToString(this._iframe.contentDocument);
             if (!htmlString) {
                 htmlString = await (await fetch(Utils.CorsProxy(this.webField!.href))).text();
             }
             this.layoutDoc.thumb = undefined;
-            this.lockout = true; // lock to prevent multiple thumb updates.
+            this.rootDoc.thumbLockout = true; // lock to prevent multiple thumb updates.
             CreateImage(this._webUrl.endsWith('/') ? this._webUrl.substring(0, this._webUrl.length - 1) : this._webUrl, this._iframe.contentDocument?.styleSheets ?? [], htmlString, nativeWidth, nativeHeight, scrollTop)
                 .then((data_url: any) => {
                     VideoBox.convertDataUri(data_url, this.layoutDoc[Id] + '-icon' + new Date().getTime(), true, this.layoutDoc[Id] + '-icon').then(returnedfilename =>
                         setTimeout(
                             action(() => {
-                                this.lockout = false;
+                                this.rootDoc.thumbLockout = false;
                                 this.layoutDoc.thumb = new ImageField(returnedfilename);
                                 this.layoutDoc.thumbScrollTop = scrollTop;
                                 this.layoutDoc.thumbNativeWidth = nativeWidth;