Using this guide : viewtopic.php?f=35&t=30870
Remove door card, reattach the window switch and wind the window down till the 3 window securing bolts are revealed where the holes are in the door. Then check whether any of these are loose. If so then bear in mind the window may need to be re-alinged and a window reset done.
If this is not the case then check all the other fixings are secured in place as it could be the whole mechanism loose perhaps?