Naim Nait 5i Intermittent Channel

I'm looking for some help troubleshooting a problem with my Nait 5i. The right channel is intermittent. I've narrowed it down the the amp channel by trying different source inputs and switching speakers and speaker cables.

I experienced the problem once before and took the system apart and reassembled. That seemed to solve the problem but now it's reappeared. I opened the amp and there was no visible damage to the circuit boards or connections.

Any ideas on troubleshooting? Any known problems with this amp? I'm suspicious of the speaker cable connections and wondering if there are known problems there.

Just looking for some ideas before seeing the dealer for service.