I had the same issue today, but with my mic channel. (Nothing too embarrassing, my coworkers just heard me laugh a joke that was made in the meeting ). In UC, I have my mic muted and am using REAPER to pass the mic signal to Zoom through the "DAW" channels in UC. But apparently, even though my REAPER tracks were muted, the signal from the Mic Pre was live through Zoom. I assume this is not expected behavior. If it is expected behavior, apart from plugging the mic into a separate device that can be muted, is there a workaround?