It sounds like the contacts under the buttons are old. This can be repaired, but I wouldn't have a clue as to how to do it myself.
My repair guy gets about $35 just to open up a kb ( and that's cheap! )...... the rest is subject to time and parts.

If you really need help - in the future, post your questions at the general arranger forum. You won't get as many smart a_s_s remarks.