I've got this Fender Princeton 112 plus combo amp , I really like this amp , however its developed a problem where after a while of playing the overdrive channel jumps in volume quite significantly , I've tried cleaning the pots with contact cleaner but that hasn't helped and I don't have a great knowledge of how amps work.

Has anyone else had a similar problem ?

Or any ideas on how to resolve it?

I have a similar problem with my amp. It's pretty intermittent though. If I play with the knobs for a while it goes away.