I'm having the same issue with my car with the windows rolling 1/4 of the way down. The annoying thing was that I didn't have the issue until 2 weeks after they replaced the window motor under warranty because they thought there was something wrong with my original motor. Now, just out of warranty BMW charged me for replacing some other component to attempt to fix the issue. Another 2 weeks later I'm getting the same issue consistently. Looks like i'll be needing another window motor and still not be guaranteed to fix the issue!
MY09 135i AW - Black Boston Leather | Manual | Sunroof | Hifi 10 speaker | Heated seats