The posts by others on this problem were right on -- there truly is
a variety of things that can affect tempo.  After suffering all the
problems mentioned while restoring old player pianos, I have learned
a few steps to avoid some of these problems.

1. Attach a small vise grip to the tempo rod while installing new
leather nuts so the rod does not turn to cause the tempo slide or
attachment to turn.

2. Bend the slide springs up a little to ensure firm contact of the
slide to the slide surface and lubricate tops of spring surfaces with
wax.

3. While the inspection cover is off the slide and rewind accelerator
area, I take outside measurements of the distance that the rods are
protruding for both of these slides and write with pencil on the outside
area that will be visible with everything installed an "O" measurement
when these slides are fully open and a "C" measurement for when they
are fully closed. (You will not find this tip in Reblitz.)

Best Christmas Regards to all fellow restorers!

Larry Schuette - The Player Piano Man
Raymond, Nebraska