white lithium grease spread copiously on both sides of the tracks solved my wife's R53 sunroof problem after the dealer claimed the tracks were worn out and that I'd have to get a new sunroof.
I'd clean the old grease off with a rag and some wd-40....bet it has a few years with of dirt and grime....then re-grease it...bet a good syenthic waterproof grease would be fine...red or even blue grease....just a few dabs will be all bit needs!!
Yes...you need to grease the rails from time to time. Also, when my car was about to go out of warranty (a few years back), the dealer drilled some holes somewhere to allow for better drainage of any water that might get trapped in there.
Thanks I bet these hints will be the cure. It gets better after a rain so I'm sure these will do the trick. Much thanks.