Roger,  A very likely cause of your problem is that the bellows are too
stiff, and that is most likely caused by the silicone seal applied to
the cloth.  At the very least he should have used orchestrion type
sealer instead of bathroom type.   Obviously the original restoration
was done with cloth that had pin holes and the restorer used the sealer
to seal them.  What else would you do?  It says "Sealer" right on the
tube!

Actually, you might be able to do that successfully, but you would have
to thin it down 3 or 4 to 1 with solvent.  Even then, it would probably
be too stiff for these small pneumatics.  Pliobond would also do the
job, and better -- again, very thinned.  Consider the construction of
pneumatic cloth: the 'cloth' part is very flexible but not airtight, so
they apply black rubber to make it airtight, which makes it stiffer.
As usual, everything is a compromise.

The best approach is to use better quality cloth that doesn't have pin
holes.

Craig Smith