4x4 error / pops back in park / check my fault codes

[Jakg]

I've got a 2010 X6 40d, which will pop back to park when you select drive / reverse.



It will get a gear up in the air (car is on stands), but when on the ground it'll pop back into park. And I get the 4x4 etc warning on the dash. I've got the following faults:

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I've tried the following:

• New AGM battery (registered) - old one was 7 years old
• Replaced the alternator regulator - old one was overcharging
• Changed transfer case oil (& calibrated) - clearing existing "oil wear" fault
• Swapped the gear selector lever - clearing existing fault

I'm leaning towards an electrical issue rather than mechanical.

Any thoughts?