Screen flashing on and off towards end of Zoom meeting

I was getting to the 40 minute point in a  paid for Zoom meeting that I had accessed via a browser link in Edge. During the meeting I had accessed another browser link successfully.  The screen started flashing on and off though audio was maintained.  Clicking on my touch pad only seemed to make things worse.  When I stopped clicking, I was able to hear audio and proceed with just that.

 My system was fine once I was out of Zoom.  After I researched on here,  I made sure my computer sleep settings were extended,  updated Windows and Edge, then re-tested Zoom on this website..  I  downloaded Chrome as a back-up, in case it was Edge (have deleted cached files in settings on Edge)  and I've turned off video acceleration in both.

It occurs to me as I write this that 40 minutes is the point at which a free Zoom meeting has to stop.  Would what I experienced be what you would expect to happen in that scenario.  Please does anyone have any other useful suggestions to add because I will not be able to test this until next time?

Thank you in advance