squash: use oldScreenSharesOrder for checking.

react/features/video-layout/subscriber.js

 declare var APP: Object;
 declare var interfaceConfig: Object;
 
-let latestScreenshareParticipantId;
-
 /**
  * StateListenerRegistry provides a reliable way of detecting changes to
  * preferred layout state and dispatching additional actions.
             store.dispatch(
                 setRemoteParticipantsWithScreenShare(newScreenSharesOrder));
 
-            _updateAutoPinnedParticipant(store);
+            _updateAutoPinnedParticipant(oldScreenSharesOrder, store);
         }
     }, 100));
 
  * Private helper to automatically pin the latest screen share stream or unpin
  * if there are no more screen share streams.
  *
+ * @param {Array<string>} screenShares - Array containing the list of all the screensharing endpoints
+ * before the update was triggered (including the ones that have been removed from redux because of the update).
  * @param {Store} store - The redux store.
  * @returns {void}
  */
-function _updateAutoPinnedParticipant({ dispatch, getState }) {
+function _updateAutoPinnedParticipant(screenShares, { dispatch, getState }) {
     const state = getState();
     const remoteScreenShares = state['features/video-layout'].remoteScreenShares;
     const pinned = getPinnedParticipant(getState);
     if (!remoteScreenShares?.length) {
         let participantId = null;
 
-        if (pinned && pinned.id !== latestScreenshareParticipantId) {
+        if (pinned && !screenShares.find(share => share === pinned.id)) {
             participantId = pinned.id;
         }
-
-        latestScreenshareParticipantId = null;
         dispatch(pinParticipant(participantId));
 
         return;
     }
 
-    latestScreenshareParticipantId = remoteScreenShares[remoteScreenShares.length - 1];
+    const latestScreenshareParticipantId = remoteScreenShares[remoteScreenShares.length - 1];
 
     if (latestScreenshareParticipantId) {
         dispatch(pinParticipant(latestScreenshareParticipantId));