Prestolite Starter Sticking

I've got a problem with my Prestolite starter which I was hoping someone
here might be able to help me out with. The pinion gear that engages the
starter ring gets stuck in the retracted position and won't come forward
when I engage the ignition key. It just whirs in place inside the casing.
I then have to go up front with a screwdriver and turn it by hand a few
teeth so it will come forward and engage. A right pain in the neck, I can
tell you.

Anyone else have this problem? How did you solve it? A phone call to
Prestolite tech support hasn't been much use so far.

Cheers,
Shawn