I have not done anything to fix it. It sounds like the wave memory is corrupted. It is to much trouble to send it in for repair. I have just been using the other piano sounds. It looks like this problem is becoming more common, maybe Casio knows the solution.
It is too much work to send in for repair. I was hoping there was some way of rewriting the waveform memory through the USB port. If there isn't, I will just use the other piano sounds. The grand piano sounds were the best I have heard on any electronic piano or soft synth.
What kind of information could the key sensor send to make it sound like that? The key sensor should only be sending note on/off and velocity. All other voices - other pianos, strings, organs etc. sound OK. It is only on the grand piano sounds.
Is there any way to reload the waveform memory? On the 2 grand piano sounds (concert and modern) 2 adjacent notes E and Eb an octave above middle C have developed a loud buzzing sound after holding the key down for about a half second. All other notes and voices work. I have tried the factory reset.