change in behavior could be a foreign conductive object in there creating chaos.
I had such a thing happen to a Kawai K3. When I moved the synth, set it down on its end a few times I heard something rattle in it.. powered it back on and the problems moved around..
finally I found a small pebble sized black ceramic looking object inside the synth.
When I removed it and powered it back on, all was working again.
Look for something where boards might be stacked close to each other.. something could be sandwiched in between, as was in my case until it dislodged itself.
I had such a thing happen to a Kawai K3. When I moved the synth, set it down on its end a few times I heard something rattle in it.. powered it back on and the problems moved around..
finally I found a small pebble sized black ceramic looking object inside the synth.
When I removed it and powered it back on, all was working again.
Look for something where boards might be stacked close to each other.. something could be sandwiched in between, as was in my case until it dislodged itself.