Yes, photos, please!
I am expecting to need to see the bottom end of the wiring harness, from the right hinge side of the tailgate, down into the tailgate body panel area.
The roof connector or wire run, from that right side hinge, through the headliner?
Basically, the motor and the wiring harness at that end and/or any connector that would make it possible to change out the motor.
I am hoping it simply is a wiring failure in the harness where it goes through that hinge. Since the wagon is the bass equipment hauler, the tailgate is used more than the driver's door.