I do have also a PSR-S900 and a KORG PA500. PSR-S900 started acting funny until updated latest OS. I can make a huge list of complains regarding PSR-S700/S900, so please do make start it. I have owned yamahas s30, s80, motif rack es, motif es 6, yamaha dgx-505 and all the PLG boards. never had an issue with them. I guess chinese materials are the ones to blame...