Have you checked the loom inside the rubber conduit where it crosses the gap between the A pillar and the door? The wires are famous for breaking isnide there. I had a quick look on the daughter's car when that happened and the first time, I missed the broken ones because I didn't pull the conduit back far enough.
If you can disconnect it at the A pillar end, and you have acess to a multimeter, you could check for continuity between the end on the motor and the end at the connector.