Unofficialbmw.com

[sktn77a]

Theter's a wire and a clip that attaches to the seat bottom (by the rail) that pulls the seatbelt adjuster up as you move the seat back.
The wire has:
1. come off under the seat or
2. come off in the b pillar or
3. Broken

Good hunting!

Keith

[hawaiidan]

I had this problem too. As sktn77a says, wire had been disconnected from 'b' column. There is a small pin that holds the wire and clip to the column. Removing the seat helps. Seats not difficult to remove and reinstall, though you will need a torx socket set.