Some mottors develop a 'dead' commutator bar at the park spot. The motor & gearbox is idemtical to the window lift, its possible to remove it, strip the plastic waterproofing dip off, open the motor case & clean the insulated area between the commutator bars with a jacknife blade, replce brushes etc It also takes the same aftermarket brass gear if the stock plastic one is chipped or cracked. A second possibility is the funky insulated mount for the short motor connectors: the motor is grounded because of its mounting, but they used one of the motor mount bolts as a wire support by fabricating a bakelite grommet/connector mount. These tend to split, soak up water etc & partially short. I threw mine away & used a tie-wrap. Its also possible that someone screwed around with the stock wiring and one fuse is popped. But most probably, one of the microswitches is dirty. They disassemble with those tiny screws & nuts, and then can be sprayed out with Contact Cleaner. This usually fixes things for a few years.
