Just recently I sandblasted the threaded rods on the capstans and
I got all of them mixed up, thinking they were the same.  But they
probably weren't the same, after all -- most of them work freely
but some have friction.  I just switched a few that had 'friction
to the left' with some that had 'friction to the right' and it all
works freely again.  The pneumatics are in the right place (at first
I thought I had slightly mis-aligned them).

Try to find out where exactly the problem lies.  I don't know if my
option will work for you, too; if you didn't mix up the capstans the
problem is probably somewhere else.  Good luck.

Regards from the rainy Netherlands,
Niels Berkers