I'm looking at one of these for a customer. It's progressively out of tune, from low to high on the keyboard. Starts out OK, but by the uppermost octave, it's 3 cents or more out of tune. Anyone seen this before? Any known fix? Looking, I couldn't find a factory reset routine (yeah, it is old). Contacted Casio, got a service manual, and neither one of us saw a reset in it. So yeah, it may be too old to have one. They lost their "old guy" about ten years ago, so no one knows any unpublished info there. I'm hoping someone here does. Let me know. Thanks!