I would checked wires too, cause of problem may be cracked/meltet together..... as they live on their own world...
I had some similar problem before, window went up and down, but not as dramatic as your situation.
It took me several months before i found the trouble, cables was the last thing i checked..
Did some cleaning and wiring protectant, and all works out great..
pics from door wiring:
986 Boxster
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