97 960 Moonroof won't open

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I have a 97 960. The moonroof will open in the "vent" position, but will not slide open. It begins to open, and appears to be getting stuck. It also is making a "rattling" noise that it did not make before. It seems like a horizontal metal piece in the front of the assembly is loose. Any ideas? I fear this will be a $1000 repair at a dealer