Sound degrades throughout Zoom classes

I've had an on-going problem with classes I take via Zoom.  As the class progresses, the audio degrades.  It usually begins as light pops or crackle when the instructors and guests are speaking, and ends with so much static and distortion that no one is comprehensible.  If I leave the class and rejoin, everything is crystal clear again . . . for a while.  It seems to only affect me, none of the other people on the call.  And to clarify, the static and distortion are only there while other's are speaking, and does not continue through silence. 

We've changed our internet service, upgraded to fiber, but the issue remains.  What else can I explore?

If I were only observing/listening, leaving and coming back wouldn't be such an issue; but in some cases my role is participatory, and if I cannot understand what the others are saying, then my being there is useless.  I've had no issues with multi-hour Google or Facebook calls on the same desktop with the same peripherals, if that helps narrow the field of where to look next.

Thanks, all!