who only by moving can balance

Alright, so, Zoom. Zoom for Linux.

Today I attended a departmental workshop on Understanding racism (a really good workshop! I was surprised by how good! my department's previous gestures at acknowledging and discussing racism have included e.g. a "listening exercise" facilitated by... a middle-aged wealthy white woman! this facilitator was Lesley Aitcheson, who on two hours' acquaintance I would cheerfully recommend enthusiastically) via Zoom, and experienced Technical Difficulties.

The specific technical difficulty was: every time I got switched from a breakout room back to the main meeting, Zoom lost all incoming audio. Incoming video was fine; laptop audio was fine; people's microphones were on and they were audible to others; but I didn't get incoming audio back until I dropped out and rejoined the meeting. (This also happened on one occasion when I was moved from the main meeting into a breakout room, but only once.)

I'm running version 5.1.412382.0614 under debian testing (current codename bullseye). I have more (related) workshops upcoming & would like to Solve This Problem, though obviously I'm not going to manage it by... 9am tomorrow, which is when the next one is. A quick shake of the internet doesn't reveal any obvious bug reports. Suggestions extremely welcome...