LUXMAN 117 Help Please II

[ODougbo]

I am still having problems with a vintage Luxman 117, but narrowed down the issue with one channel dropping out . From what I can see with a flashlight there is a separate board that the RCA inputs are connected and thinking there is lose connection, or cracked around the RCA because with a push - it moves slightly [down] and the sound returns.
Question, has anyone removed the far rear circuit board on a Luxman M-117?

 

[ODougbo]

I just remembered there are two pairs of analog inputs; Fixed and Variable RCAs. I moved the input cables to the top (variable) but also noticed the
mini-potentiometers are very difficult to turn, maybe a drop of silicon-oil on them?