could it possibly been changed by a songbook entry or a midi file? Have you tried a differant setting on the right hand to see if that is the problem maybe in performances. Just a thought. Sometimes just a little thing like that will drive you crazy. With me it's a short drive.
MEL
_________________________
KORG PA1000, KORG PA900, 2 BOSE S1 PROS, 2 BOSE L1 COMPACTS, YAMAHA STAGEPAS 500, ROLAND VP7