Yamaha Disklavier sustain pedal thump: turn off all power, remove the
plug, after two or three minutes refit the plug, turn on power and
recalibrate controls as per instruction booklet or web site, especially
the pedal adjustments section.

Player piano keys staying down could be simple leak in tracker bar,
cracks on the brass nipples, ill fitting tubes or holes in tubes from
mice.  After that look at gaskets then valves.

Terry Kirwin
North QLD, Australia