I recently got my parents' 70's era GAF 1788 Z dual 8 projector out of
mothballs. The old main drive belt had gotten hard and broke so I replaced
it but it's still having problems.

The problem is that when in FWD, the drive wheel isn't being pushed into the
driven disk edge on the inside end of the takeup reel spindle, ergo the
takeup reel isn't turning.

All the O-ring type belts are in good shape, the gears/pulleys are all
sound, the rubber on the edges of the nylon drive wheels is good, I don't
see any broken springs etc. The projector actually has very little use, it
was only used a few times, hardly enough for anything to get worn out. I've
studied the mechanical configuration of this thing until my eyes are blurry
but can't see why it's not behaving correctly.

Any suggestions will be appreciated.