We have many Kawai uprights at school, and most of them develop this once a year. I have mentally attributed this (with no evidence) to changes in the keybed. Our building undergoes drastic temperature and humidity changes. If I leave it alone (not that I ever would, of course), it goes away. There is usually obvious lost motion, and I have usually combatted it by adjusting capstans. That isn't always enough, though. I, too, will follow this thread with interest. Mark Graham Baldwin-Wallace Conservatory of Music Berea, Ohio
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