In the past I've used white lithium grease on window tracks. Not sure what's the best chemical. The sunroof grease is pretty nice but might be a bit thick. A credit card with the microfiber towel around it is a good cleaning tool.

I've yet to have one fail on my bimmers but have had extended battles with them in Honda and GM cars. Usually they slow down then one day at the worst possible time it falls down. Use masking tape not duct or gorilla tape to hold it up.

My driver's door is a complete trainwreck, it has an Amazon regulator that currently works, but makes a bunch of noise and runs super quick like it's on 15v. The passenger side is untouched but fairly slow these days. The rear ones are still perfect.

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'05 E53 3.0 6mt
'17 F30 340ix 6mt
'96 E36 328is, in progress