shoulder strap retractor

The driver's side (naturally...) shoulder strap retractor has stopped
functioning in my 94 SL2, with the strap in the rear position. It
tries to move a bit from time to time, but only goes up and down an
inch or so before stopping. Before I tear the inside of the car apart
to see if I can fix it, can anyone suggest a possible cause or solution
to this?

Yeah... I would clean out the old grease from the retractor track and
re-grease it with fresh one.
I've had this problem in the past, especially in winter when the grease
would harden up a bit and the retractor had a hell of a time moving. At
one point the grease was so bad that it blew the fuse on the retractor
motor.
I got so ticked with it that about 4 years ago I disconnected the fuse
and fasten up manually since then.