Looks like I spoke too soon. During weekend performances buzzing started at end of third act unless we restarted the sound software during the final scene.
None of my usual tests caused buzzing though. It’s as if the problem is now intermittent. The test that has for months reliably buzzed was to start the sound software, start a repeating playlist, and after 2-3 hours or so the buzzing would be back. This no longer happens. Before someone suggests some type of amp issue the buzzing can be heard through the QU32 headphone jack listening on the input channel, even if the amps are shut off. Also, capturing the WAV file being sent to the ASIO driver does not show buzzing. Which is why I’m pretty convinced this is happening between the ASIO driver and the QU32 itself.
I reinstalled 3.34 and now the usual trials that reliably buzzed in the past are now not buzzing, in other words, dropping back to 3.20 changed something, but going back to 3.34 did not change it back. And if the problem only occurs after an hour or two of running and then stops, well, very hard to catch.
This is exceedingly frustrating. I know it will buzz during the performance, but I don’t have any idea what will make it buzz.