[V8] Strange sunroof behavior

[Unka Bart]

G'day all,

Yesterday I got into the Gentleman's Express ('93 V8Q 5M) and opened 
the windows and sunroof to let the hot air out before going for a 
drive.  When I went to close the sunroof and drive off, it would not 
fully close, stopping approximately 1-1/2" from completely closed.

I have cycled the mechanism many times and it consistently stops in the 
same place.  I have tried gently forcing it beyond that point, I have 
tried gently rapping on it while it reaches that point; all to no 
avail.

Does anyone have any suggestions on how to cure this?  Any ideas on 
what's (not) going on?

Many thanks in advance,

Bart