There are many things that can influence the motor switch pneumatic.

1.  If you have a grand, the paper must cover and seal the control port
in the take-up spool.

2.  The left hand spool chuck must have a good seal to the take-up spool.

3.  All the  control tubing must be air tight.

4.  The repeat switch mating surfaces must be absolutely flat and have a
light film of lubricant to prevent leakage.

5.  The slide valve on the transmission must operate properly and seal
tightly.

6.  The bleed port in the motor control pneumatic assembly must be open.

On some grands there is also a "T" in the line, between the transmission
valve and the cutoff block, that has a built-in bleed.  Make sure it is
there, and clear and properly connected.

I hope this helps in your trouble-shooting efforts.

Bob Lemon¶
Lemon's Player Piano Service¶
Sacramento, CA