This is a long shot, but I can't seem to find anything elsewhere online about this specifically as an issue.
I have a contrast problem with my backlit MGB. When I use it, the contrast consistently fluctuates without me touching the slider. It seems to sometimes be triggered by pressing the A and B buttons, and sometimes it isn't, and instead gets triggered by sounds or changes on the screen.
Furthermore, the contrast gradually gets brighter as it's used, rendering it completely unusable after half an hour of playing with it.
After I turn the system off, it resets to a normal contrast level after a while, but when I turn it back on it immediately starts up with the same issue.
From what I've found online (though my search only found various DMG contrast problems) I should attempt to clean the wheel and general surrounding area. I'll try that ASAP but wanted to make a post detailing the problem to see if anyone knew of any particular causes that might have come to mind beforehand.
Thanks in advance!