mulveling
"However, physical contact connections in the audio chain can be very tricky. If you have a single bad contact, it can very easily cause problems like (say) L/R channel imbalances."
so true. the basis of my comments to OP
1. I changed all my RCA cables to Locking RCA jacks
2. If Balanced option available, even for short residential use (normally balanced not needed unless long runs), I use the balanced because they are locking connectors
3. my vintage McIntosh mx100z had slightly small diameter, and corroded rca jacks, Audio Classics replaced all the RCA Jacks with new gold plated ones, hooray!