Check that the dampers are not raising too high and hitting the belly rail. It could also be, too loose pinning in the bird's eye, loose knuckle glue joint, loose hammer glue joint, jack hitting the end of the wippen window or backcheck hitting the sostenuto rail upon release. There are so MANY sources it is impossible to list them all. Get out the old ears and listen, feel, test, isolate, think (painful as it may be) and look. Lots of luck. Newton
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