Adcom GDP500II help for intermittent channel failure

I’m back for some help. Have a channel that sometimes works for a while then stops.

I’ll check the output jacks and give it a good cleaning. But was looking on some input of what to check for? Does it sound like a cap issue or ??

The amp itself is good. Switching RCA connections between preamp and amp pointed to the preamp being the culprit.

im a real newbie at these types of repairs but enjoy doing a DIY fix. I was able to fix the FM unit on this by replacing the CT104 by threads here as an example.

looking forward to suggestions.