DENON Input selector jumps randomly

Question

I have DENON amplifier PMA-980RIt does a strange thing. The input selector button(CD, Tuner,AUX, Data etc) jumps like crazy from one selection to another and I have to turn it of. It does it randomly and sometimes stops, sometimes won't work for days.I can't found any pattern as when it does it.Can you , please help, as it is a fantastic amp and I really want it fixed.Thanks Vesna