First thing to do I quess is to check all the wires between the powersource-switch-el.motor (with the use of elect. measuring eq). Check if any fittings are loose.
I think I would first check the switch and the wires running from the body to the door. That's where the most movement is.
Tape down the button and start wiggling. With any luck the wires that are damaged make one final contact and let you know where the problem is.
J.D.
August 2010