HAHAHA, Ok guys, I saw this thread and I was like...dude...I thooght I was the only one that had this problem.
Actually, I still have this problem and I just live with it because I do know HOW TO get my window to work again. All it needs is a quick adjustment.
Our cars or any BMW with the frameless window does down about 1/4 inch when you open the door, and goes back up when you close the door. The problem is that, overtime, the "gap" that the window goes down when you open the door gets smaller and smaller, and eventually there is very minimal gap. (I do not know how to eliminate this "reduced gap" from happening, maybe BMW engineers can fix this). This is when the problem happens, the window is at the maximum position. And if you try to close the window, it will bounces back because it hits the limit.
Now, all you need to do is...roll down your window with the one-touch function, and once the window stops, you will see that the window is not fully in the door
(a small amount of window left, this happens only when you have the "window bounce back problem"). Now push the window in with your fingers
and roll up your window back up with the one touch function...and wala...you just re-set the window minimum position and the problem went away.
I have this happen many times. I now just prevent the problem from happening (when I notice the "1/4 gap" gets smaller) by doing a fully opening/closing window cycle. You don't need to push the window in with your fingers, only needed when you encounter the "window bounce back problem". Works everytime...
I think some people never experience this problem because they fully open their window at least once a day. And as soon as you do this, it re-sets the window position. Personnally, I hardly open my window at all, that's why I have to do the reset from time to time.