Just a thought: I have serviced many of these over the years and
often I find that the motors and gears, etc., need lubrication very
badly.  The shafts become gummy and don't want to turn.  I have used
light lubrication like WD-40 to start out with, and after it's freed
up I use a light machine oil.  Again, it's just a thought.

Jim Jelinek - Player Piano Clinic