Mc4000 microphone 2 cuts out and quits working

Has anyone ever had issues with the Denon mc4000 with microphone issues. Works fine on mic 1 but after about 20 minutes mic 2 quits working. I have to cause feedback to get the channel back up and running. Then the channel is distorted. Any ideas? I started a ticket with denon already. Just want your thoughts.

Not heard that problem before. What mics are you using? Not impossible that it’s just a technical fault in the gear of course.