CPU usage for Zoom > 35% (actual meetings, terrible perf.) and < 6 % (test meeting, OK)? Please help

Recently, for maybe last 2-3 weeks, I have a very difficult time with Zoom meetings. The CPU usage hovers around 35%, video freezes or keeps going blank, sound is so scratchy I cannot understand a word or just freezes. I tested the meeting with Test Meeting at Zoom, and sometimes the CPU usage was barely 5-6%, sound was clear as a bell, at other times I had the same problems as with "real" meetings.  The size of the meeting does not matter, though the meetings with local attendees do not suffer from these glitches. I have not made any conscious changes to my system in the last 2-3 weeks.  Before these problems started 2-3 weeks ago all meetings were crystal clear and I had no problems whatsoever. Also, Google Meet and MS Teams are not affected, still working great as far as sound and video are concerned.  Same meetings on Zoom on my Android 10 phone are also still flawless.

I thought maybe my computers drivers need attention, so pointers to a good way to check and update the drivers would be welcomed.

Overall I would appreciate ideas or suggestions on logging the performance issues, and where to look or how to solve this problem.

Thanks!