Has anyone attempted the repair of these things?

After about 10 years daily use our door motor began to continue running
for about 30 seconds after the door was fully closed/open.

I then made the mistake of holding and then releasing the door as it was
descending. Gravity quickly took up the slack and appears to have
fractured the connection between the frame and the drive motor.

I think removing the door collector roller and the motor is easy enough
as the door slats appear to be retained by several swivelling rods which
are themselves retained by large pop rivets. But what then?

The only identification I can see is *40 M* on a little yellow label.
This does not link to anything on the Hopkins site. The people who
installed it are not overly enthusiastic about repairs (I guess there is
more profit in new installations than repairing old ones).
--
Tim Lamb