Yamaha DGX 220 Chords not playing correctly

by Ethel
(Spain)

Hi to all... hoping someone may give advice on my old keyboard. I have been having problems with notes not playing and playing loudly etc. but I have used a liquid to resurface them, all seems okay except I have a problem with chords not playing correctly. If I use the short chord for Am7 it mostly plays G sharp 7..... unless I press the G note slightly after the the A and A flat, and if I play the full chord Am7 chord it quite often plays a C!! It's driving me crazy. Anyone have any positive remedies? Thanks in advance. ethelread@mail. com