2012 BMW 650 Convertible - Driver's Side Rear Window Closing Ploblem

v312155

In the last 18 months I've had problems closing the driver's side rear window when closing the canvass convertible top. This happens approximately 80% of the time. I've had it back to the dealer, under warranty, three separate times, and still have problems. When the top completes the closing cycle, the problem window attempts to close, but then proceeds to open about 25% of the way. I need to step out of the car and pull up the window by hand, while pressing the window button. Anyone have suggestions? Thanks!