Keyboard and mouse suddenly unresponsive in working area - consistently after +5 minutes working

This was an intermittent problem with previous versions, then it would just go away.

Back with a vengeance on this new version. Can be working for any amount of time from 5 mins to hours, then suddenly can't use keyboard shortcuts, i.e. zoom, etc or the mouse won't react within the work area. I can access tabs and menus fine, but not anything on the working canvas. Alwayd have to quit and restart.

I've dumped prefs a number of time, etc, as previous problems have advised. This has happened 4 times already this morning. Did the same for one day last week too.

On Catalina 10.15.7.

Any known issues? Doens;t look like a keyboard problem if the mouse is affected too. This is only happening in Photoshop, nothing else. No other software which is running that conflicts either.

Anyone else? Any suggestions please?

Anth