2002 Dodge Caravan window regulator motor

Why would a window regulator motor that was not working suddenly start working again after loosening and then retightening the metal motor casing? The driver side motor was not working at all. All I heard was a single click from the switch, not noise from the regulator. I pulled the panel and the switch was putting out 12 volts. Tried to remove motor, but accidentally loosened screws that just held the metal cover over the motor shaft. As soon as soon as I saw the motor shaft, I tightened the screws back up. Not sure why, but I reconnected the connector and it started working again. I did not touch the regulator cables, just partially removed the metal cover of the motor. I assume it is going to die again soon, but I will wait until then to replace it. Napa sells just the motor without a regulator. Is there any reason not to replace just the motor?