There is an internal thermal overload relay built into the motors. If motor tries to keep running against the stop, the relay will trip and motor will not run again until it cools down. Sometimes those relays fail, and then people think the motor has died when all it needs is a new relay.

There is a thread here about this subject.

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Graham
85 300D,72 350SL, 98 E320, Outback 2.5