Marshall MG50FX Channel Switching Issue.

[gtrplayr1976]

I have a friends MG50FX that will randomly switch from clean to overdrive ,and back to crunch. It could do this once ,and not again for awhile , or it could do it repeatedly. Only thing I've found is on a different model where it talks about the switching circuit malfunctioning. Could be what this is doing ,but I can't even find schematics. I have no idea where to start on this. Has anyone had any experience with this?
Thanks !

[Enzo]

First reaction is clean the cutout contacts in the footswitch jack.

[gtrplayr1976]

First reaction is clean the cutout contacts in the footswitch jack.

Thanks Enzo. I will give that a shot. Just a note: It does this with ,or without the footswitch.

[gtrplayr1976]

I cleaned the footswitch jack. The amp has been on now for over 1 1/2 hours ,and is still on the clean channel. I'll leave it on for awhile to see if it holds ,of course it could hold all day ,and change tomorrow I guess.
I have now noticed the green (clean channel indicator) is flashing. I don't see anything in the manual about this ?