It may take more than a re-set to cure that problem. I have just replaced the motor on the driver's side, since the window was failing to drop or wind down intermittently. When I had the old motor off the car, I stripped it down and discovered that the brushes were badly worn, one had almost disintegrated and the commutator was covered in carbon deposits. I am now looking for a set of replacement brushes so that I can re-condition the motor and either keep it as a spare or sell it on.
If anybody knows where to source a set of motor brushes to fit, I would appreciate a heads-up.