I don't have a final solution, but here are some things to check...
Start here to understand the system, it could be several things:
https://www.newtis.info/tisv2/a/en/e...ration/XTgUlge
Check misalignment or loose fasteners:
https://www.newtis.info/tisv2/a/en/e...-locks/FmwKRQ6
https://www.newtis.info/tisv2/a/en/e...-locks/FkCn42Y
https://www.newtis.info/tisv2/a/en/e...-locks/FmCL9aI
https://www.newtis.info/tisv2/a/en/e...locks/1MAEZtRF
IF it's the the lower tailgate microswitch (51247183196):
https://www.realoem.com/bmw/enUS/sho...57#51247183196
When the tailgate is closed, tailgate contact switch switches to earth. The status of the tailgate contact switch is evaluated and made available by the junction box electronics
The contact of the lower tailgate is designed as a microswitch and it switches to earth. The status of the microswitch is evaluated by the HKL. If the lower tailgate is not correctly closed, the automatic luggage compartment lid actuation cannot be executed. The automatic luggage compartment lid actuation control unit generates a Check Control message.
Another big part is the automatic luggage compartment lid actuation control unit. Probably pricey.
Good luck.