Tail gate / rear hatch / "trunk open" message

[e39driver]

2011 X5 3.5i Premium with backup cameras.

Just started receiving "trunk open" message.

All tail gate operations seem to be working properly:

- dash trunk open switch works
- key fob trunk open switch works
- tail gate open height adjustment on iDrive works
- tail gate push-button switch to close works: tail gate closes and then there is a secondary closure that brings the tail gate flush with the rear quarter panels.

I've tried pushing in on the tail gate (after it is closed) and there is no further movement (wouldn't expect so as it is flush with the rest of the body panels).

Could this be a sensor issue?

Ran a scan with code reader - no codes showing.

TIA,
Ken