I'am having similar symptoms. Relay clicking and loss of right front and right surround channels. Problem occurs when amp heats up. With cover removed problem occurs but only after an hour or so of use thus pointing to a thermal problem. When I press firmly on the left most (large black vertical capacitor)on the mother-board the channels return .. let go and the problem returns. It's obviously an area of the amp that delivers DC power to the final amps using what appears to be a buss-like rails.

Anybody know how to get a peek at the bottom of the main pc board. I'am looking for a cold solder joint or hairline crack in a land in the area of the capacitor.

Any body have a funcional schematic the documents functions of the offending area of the main circuit board?