It's possible the area surrounding the switch shrank to where the button becomes inop. In my home, some of the doors get too "tight" for their openings in the winter, giving the impression that the door has expanded, but it is the other way around.
Only hole in this theory may be that the heat of the amp itself should compensate for the cold environment, but who knows as to location...
Only hole in this theory may be that the heat of the amp itself should compensate for the cold environment, but who knows as to location...