Remote not working

[lestat]

I've been having this issue for a while now and I can't get to the bottom of it. Basically, the remote stopped working, and won't sync. Central locking button on the center console works fine.

Things I've tried so far without success:
- Another diamond keyfob (all keys have good batteries)
- Replaced the diversity amplifier in the D pillar (e39 touring)
- Replaced and coded the GM3
- All fuses good
- Unplugged the fuel flap actuator
- Unplugged the hood sensor

I had a look at INPA but it doesn't tell much about remote locking. However, I can see the status of the anti-theft sensors (tilt, hood etc.) and there is a particular one that shows as being 'on' - "WINDOW SURVEILLANCE REAR" and seems to be active on the driver side, and off on the passenger side. Is this sensor stuck in the 'on' position and causing all the trouble? And what sensor is this anyway? Or is the fault somewhere else and I'm chasing a red herring?