There are quite a few posts on this forum about this. First I took my door apart, then switch area, then tested volts to the motor= 1.5 volts, not the motors fault, its not getting juice.
After reading a bunch of posts it became much clearer, and after talking w Tom at index the body module begins to fail at a certain number of hours vs miles. The oldest of our cars are fast approaching 10 yrs old and we are on the forefront of future maladies. Spoilers go up, windows stay down and who knows what else. Particular care was given to the two points in the front where ground wires converge and attach to the body, those need to be cleaned too. My car has spent its life in SW TX and NM, no corrosion anywhere.
To rebuild for 280 frt included w a lifetime warranty sure beat any other alternative out there including ebay.
I'll let you know if it solves the problem.