[msej449]

It's pretty unusual - I think that this is the first time I've seen this posted as a problem in four years of forum membership.

There are a number of useful threads on convertible soft-top fabric maintenance that would be worth looking at. Some key recommendations:

Lubricate the window rubber with Gummi pflege - this is a rubber lubricant that keeps the seal soft.

Don't fold down the top if it's wet. Unless it's just for a very short period. Always have it dry before you put it down for any length of time.

Ideally, keep the roof up when the car is parked for any length of time, so as to keep the fabric under tension.

At least twice a year, clean the fabric with a fabric cleaner and then re-proof it. BMW do concentrates for this but there are plenty of 3rd-party products as well. If it gets hit by serious bird strike or heavy tree sap give it a clean. And like all windows, if the glass isn't clean it can resist closing fully. So best to clean - inside and out - then lubricate the window rubber, and then take a look for gaps.

The only soft-top issue that I recall on the forum was where the fabric hadn't folded as it should which had caused a tear/broken crease above the window made by a metal part of the roof mechanism. Perhaps yours has a similar problem. Might be worth doing a search of the archives.

Because the convertible glass has to drop every time the door is opened, it can sometimes make the closing mechanism more prone to misalignment i.e. it doesn't shut fully. Although normally, the gap is substantial and obvious. But that may be worth checking too.