I rescued a beautiful 4.8i almost 2 months ago that I have been going through. The major issue that it had was when cold, the shifter constantly throws itself into park or neutral if you are going over 4mph or so throwing the 3 lights and numerous codes. Very dangerous to say the least. When 'something' warms up, it drives like a dream with no shift selector issues and zero codes. For it to get warm enough to drive we are talking idling for 25-40min. I've been searching forums, videos etc and haven't found anyones doing this exact thing.

Video of the issue: https://youtu.be/s_-cG88dE1M

What I've done so far:
new battery (vehicle was on its third one but still thought it had the original one)
purchased battery maintainer.
new alternator (didn't like the readings I was getting)
new transmission pan/filter, bridge seal, 4 rubber valve seals, mechatronic sleeve
pulled servomotor and inspected plastic gear inside which surprisingly looked good.

So I don't know if it's a ground issue, something in the mechatronic computer, servomotor or the gear shift selector unit itself. Just not real sure anymore it won't make it more than 5miles right now before acting up terribly. Any help would be greatly appreciated before I start throwing serious money at it. I've attempted several times to post on bimmerfest but after 2 weeks still will not let me post.