Index: openacs-4/packages/proctoring-support/www/resources/proctoring.js
===================================================================
RCS file: /usr/local/cvsroot/openacs-4/packages/proctoring-support/www/resources/proctoring.js,v
diff -u -r1.1.2.18 -r1.1.2.19
--- openacs-4/packages/proctoring-support/www/resources/proctoring.js	20 Dec 2022 15:20:54 -0000	1.1.2.18
+++ openacs-4/packages/proctoring-support/www/resources/proctoring.js	2 Jan 2023 15:26:01 -0000	1.1.2.19
@@ -364,6 +364,7 @@
         this.prevPictures = [null, null];
         this.streams = [null, null];
         this.videos = [null, null];
+        this.canvases = [null, null];
 
         for (let i = 0; i < this.numStreams; i++) {
             const streamName = this.streamNames[i];
@@ -694,7 +695,10 @@
             const pictures = this.pictures[i];
             const prevPicture = this.prevPictures[i];
 
-            const canvas = document.createElement('canvas');
+            if (this.canvases[i] === null) {
+                this.canvases[i] = document.createElement('canvas');
+            }
+            const canvas = this.canvases[i];
             canvas.width = iWidth;
             canvas.height = iHeight;
             const ctx = canvas.getContext('2d', {willReadFrequently: true});