I decided i couldn't wait and took a look today
Ran through the setup checklist and did not find any issue on the amp board. I unplugged the input as you suggested and just had a faint humm/buzz.
I plugged just the left channel back in and was able to adjust the volume normally. Added the right back and it was still full blast and seemed to be leaking into the left channel (or that was my brain).
I then spun the volume knob around a bit and in some spots the right channel cut out completely and there was more static type audio noise while moving than i recall in the past.
I then put the rca inputs directly into the amp board inputs bypassing the volume pot completely and controlled the volume on the mp3 player. Amp sounded normal and both channels were fine. With no source connected there was some light buzzing/noise, but as soon as the mp3 player was connected it went away. Though there was a ton of noise inserting the 3.5mm into the mp3 player (guessing that isn't good for the amp, and i should power off before doing that again).
I pulled the pot board out and took a look at it, but nothing visual looks bad on the solder joints. I forgot today to put the multimeter directly on the pot connections. I'll take a look after work tonight or tomorrow when the wife is gone