Yeah... that makes sense. Thanks!

I pulled everything from the stack this weekend and visually inspected
everything I could see... As mentioned in a previous response, every
single screw, holding in every tray, had a nut on the back of it, and
half of them became part of the permanent W/B! I took an air
compressor with me, along with the component/connector cleaner and
cleaned every connection I could. I'm going to hold off on putting the
trays back in and borrow the tools from my mechanic to do it right,
rather than figure out how I'm going to hold nuts on the back of trays
for each screw.

While I was working on this, I ran into someone up at the Ghost-town
(err, I mean Georgetown) airport that I haven't seen in a while. He
offered to let me swap out and try his audio panel, to see if that
might be the culprit! As soon as I get the trays back in place and can
reseat all of the avionics devices, I'll give it a quick check flight
to see if I can get it to fail again, then try the replacement audio
panel.

Thanks for all of the responses, and I'll provide an update when I can.

Best Regards,
Todd