I had the same problem with my 97 528. The slot that houses the divit starts to bend after awhile, giving room for the divit to slip out. I tried 'JB Weld' to hold it in place, but that eventually gave as it did not allow any movement with the curve of the track.
I ended up replacing the regulator as it comes with the track and motor in one piece. I bought mine at a local recycling yard that specializes in BMW parts (
Bavarian Auto Recycling ). It cost me less than $125 and came with a six month warranty. The dealer wanted $226.00 for a new one.
It took about 2 hours to replace as I was following the instructions in a Bently manual and realized that they left out two steps in the process.
Good luck.
