I've been having a lot of trouble with the sustain pedal on my Mark I Stage Seventythree from 1980. No matter how tightly I screw it in it always gives poor and uneven sustain and gets loose after about three taps! I'm a pretty handy guy and have fixed my Rhodes into great condition otherwise, but I can't figure out what to do for the pedal. Is it fixable or should I take it in to a professional?