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It is a little bit more complicated, probably because it is old and ment to work forever :). The carrier is almost like a black box. Inside it is a seperate motor which pulls himself back and forward on the chain. This motor is ofcourse protected. If there was a safety cord present, I would just have to pull this cord which would detach the motor from the chain.
Just give them another call. I will know tomorrow if they can replace it on Friday. If not, it will be for next year.

Ah, okay. Well, good luck with that!