pianodad

Can you share where you received that info, and/or what it takes to fix? Also, do you know if midi output is affected but the issue? If not, shouldn't it be possible alternative to replacing internal electronics would be to output midi to an external sequencer (or similar device), and route that to speakers?

I've got the same issue as the OP--buzzing sample defect on medium-loud presses of three keys when using acoustic piano sound samples on my PX780. This really feels like something that can and should be fixed by a firmware/sample update from Casio!