A streaky film appears on my windows after lowering while wet. Can't figure where it's coming from. Took the door panels off and found nothing of significance. Perhaps the rubber
guide on the door? Glass sometimes screeches when lowering on hot days as well.

 

I would guess your 'dew wipes' have gotten some sort of oil/chemical on them and it transferring it onto the window. You could try cleaning with a mild degreaser/Dawn with the window down or you may end up having to replace the window seals. At least that would be my top suspect.

 

I would check those window felt seals, they get grim on them and need cleaned. One is on the outside and one on the inside. Number 1 and number 4. I clean them with Windex and a cloth and dry. Its that felt rubber that touches the glass.

https://www.realoem.com/bmw/enUS/sho...diagId=51_9299

https://www.ecstuning.com/Search/Sit...h/51337299991/



https://www.ecstuning.com/b-genuine-...l/51335a4cf95/