Channels Switch by themselves?

I would examine the pushbuttons at the front of the PC board to see if they have been contaminated with any kind of liquid that was sprayed or spilled inside. If they are contaminated then you can try cleaning them with lacquer thinner or replacing them and cleaning the board. If they are clean then this is a symptom of a defective main computer IC, and I have seen this on many of these sets. Unfortunately, this IC is surface mounted on a sub board and the board would have to be replaced and reprogrammed, and this would have to be done by someone with experience in these sets.