Update:
So after the car sat - battery drained because of some cold weather causing the car to go brain dead then revived by the trickle charger, restarted it, cleared the error codes, recoded the transmission, xdrive, and gearshifter along with the parking break to factory and reset all the adaptations, the car does move forward and backwards normally again...

*but*

Still a grinding noise when going from reverse to park or from drive to park.
Does not do it going from drive to neutral or reverse to neutral or neutral to park.

Reading around, it seems like a common issue - but without a causative solution.

Obviously it appears there is something spinning from drive to park that is causing the parking pawl to grind (possibly may even be broken as the car will still move when in park).

Anyone have any experiences relating to this and what was your solution?