Catalina - Video (& Audio) stop often and don't work for a while
I don't know if this is an answer, writing here because I cannot comment yet.

I had the same problem since yesterday. within 5 mins, both my video and audio would freeze and would work fine within the next 2 mins. I tried a bunch of thing. Which might have fixed the problem. 
 1. I was postponing my Catalina update. When I encountered this problem, I went ahead and updated it.
 2. I made sure I switch off my bluetooth while not connected to other devices.
 3. I figured Snap Camera was the real cause of this whole problem. The first time I encountered the problem was when I was on a call and tried to stop/quit snap camera that was running behind. So getting rid of it may have helped. 
I will continue to test it and post any updates I find.