My 6101LM is changing channels on its own! HELP!

[StrumFunky]

Hello all, I trust that all is well!

I'm having some major issues with my 6101LM combo, to the point of actually not playing it for some many years now. I miss the sound/feel of it, so I'd like to put it back into service. The latest/last problem that I'm having with my 6101LM is that once it's warmed up (and played through for about 15 - 20 min., or so), it changes channels on its own. It'll switch to the "Crunch" channel, and I'm no longer able to select the "Clean" channel at all. I can select the "Lead" channel, but the amp will switch right back to the "Crunch" channel in a minute or less. Any assistance that anyone could lend would be most appreciated.

[Mike_LA]

Does it happen with the footswitch plugged in?

[StrumFunky]

Does it happen with the footswitch plugged in?

...haven't checked it with the footswitch, Mike (...don't know why I never thought to do so). I'll check it n' holla' back. In the meantime, what could the problem be if it behaves the same way with the footswitch plugged in? What could the problem be if it works fine with the footswitch?