In terms of repairing players, I hope this bit of information might
be helpful.  I have found that the drive end chuck on late Aeolian
players has a circumference that is slightly larger than most.  This
larger size combined with the smaller inside circumference on certain
spool ends causes the roll to be situated too far to the left for the
tracker to work properly.  The simple repair is to put the player in
reroll mode without the roll and press a file to the drive chuck as
it spins.  Until I figured this out, it would drive me nuts why some
rolls would track properly while others not.

Don Barton - Barton Player Piano Co.
Minneapolis, Minnesota