Technically, clearance is clearance hehe
Yea, I have seen this 'transmission range switch' fix mentioned which sorta could be it (other than the clunk that occasionally happens). This was a clearer video of it done on a different transmission but the same kinda thing is in mine in the Z4 transmission but that guys video was less clear.
View: https://www.youtube.com/watch?v=qXkLjefUYU4&list=LL&index=1
The valve body repair would be nice if that is what it is, not sure a valve body can be bought new (probably not). If new, that thing is probably a few grand. A repair would be fine by me if that is what it is.
I have also heard battery replacement and alternator check because a low battery or an alternator not putting out enough juice can do funny things.
Realistically I wish there was a transmission specialist locally but not sure there is one so for the time being I will have 'my guy' at BMW chase things down; fortunately I am not getting hammered for costs....yet.
edit, can't seem to 'spoiler' the video and have it work, so just linky