Yes it seems to be a common problem as they age, especially if often exposed to the elements.
Garmin's lack of enthusiasm when it comes to repairing an otherwise perfectly working device is somewhat disappointing, but that's Garmin.
Apparently some people have had success with the original button's hole using pencil erasers trimmed to the right size/shape and held in by ducting tape, others have cut a pencil eraser or a piece of rubber to shape, placed it in the hole and used silicone to hold and weatherproof it, and I have read that others have just used some type of silicone only, which apparently works for a while.