Thank you for the write up!! I had the same symptoms, did the zip tie fix and it worked! However I have a few things to add (2005 330xi):
• I skipped step 11 as the mirror module is behind the insulation
• I skipped step 13 since I am fixing the rear slider, the front does not need to come out
• CAREFUL when using tape to hold up the glass, I used packaging tape and it peeled away my tints. I then realized the window is snug enough to stay put by itself.
• Step 16 I only removed the 2 bolts for the rear slider
• Lastly, I tried the first original method of using two zip ties parallel to each other, but it wasn't tight enough for me and there was still play in the slider and the window would still get caught sometimes, so thanks to the video below, I criss-crossed the zip ties so there won't be any play.