This problem could be a number of things.   I suspect there are leaks
somewhere.  Will the rewind function if the bellows are closed manually,
and held in place during rewind?  If so, the gears may be okay.

There is a possibility that the valve lock and cancel is not functioning
properly.  The rewind bellows unit should be removed and checked at
your work bench for leaks, not only in the bellows cloth, but the
gasket that holds the rewind box and valves together, and the valves
themselves.

Often during the heating season, wood will shrink slightly and allow
small leaks around the edges of the valve unit, and very slight
tightening of the wood screws that hold the unit together are all that
is required to get it functioning again.

The other possibility might be the small gears are worn, and one or
both may require replacement.  In addition, there are adjustment screws
that will raise and lower the rewind pneumatic.  This adjustment must
be precise for the rewind to function correctly.

If you are unfamiliar with this unit, trying to "patch" it might do
more damage than good and you should consult a professional.

Bruce Clark