We never bothered delving into the inner workings of the sunroof motor and simply replaced them when their "park" positions were blown out. So long as it is timed correctly the function that allows the motor to stop in the closed position whether it is coming down from the vent or closing from the full open is an internal feature in the motor. Unless someone has had luck taking one apart and fixing that feature inside of the motor I would say that your only option is to hang a new motor. YOu might want to consider replacing the switch as well. Part of the mechanism in that switch is plastic and it melts after time and can cause the motor to burn up as well, I've seen that one happen plenty.

Mark