This isn't an answer - just a confirmation that this is also an issue with my setup. I have a PreSonus StudioLive 32SC connected to a MOTU AVB network (two MOTU UltraLite AVBs, one 16A and one 8A with a MOTU AVB switch).
Strange things definitely happen when I manipulate the gain on my StudioLive. It's not every time, but often. It doesn't matter which channel it's manipulating, just twiddling the gain will cause the MOTUs to drop out - not just in terms of audio, but also their web console disappears for a moment and sometimes they re-enable with a totally broken sample-rate requiring them (the MOTUs) to be disconnected and reconnected to their respective computers via USB to get the audio to work fine again.
I'd love to know if this gets addressed and I'm very happy to help debug/test things. :-)
I can also confirm that this is an issue with both the 2.1 and 2.2 firmware versions.
Other than this issue I've been sooo happy with the StudioLive 32SC!