Microphone freezing as Host

I have been using Connect for 2 years and have never previously experienced this problem:

As Host, running an online session with 16 participants, my microphone regularly freezes. The mike icon displays green but without the 'airwaves'.

This happens even with excellent network health.  I am running version Mac2022.10.42.64 on a 2022 iMac

I use a Sennheiser headset.  I have tried disabling my (Norton) firewall.  In Mac Systems Settings I have allowed Connect access to microphone and camera.

This is obviously a very disruptive glitsch and I'd welcome informed sugegstions.  Many thanks!