Flip out screen door sticking
Sounds like you have a broken gear. Use the search function as there is probably 3-5 threads dedicated to this very issue.
Keywords:
Nav screen, MMI screen, gear fix, or nav assembly
Thread closed.
There is a seller on Ebay who will fix your faulty mechanism by return if you send it to him or someone else who will sell the driver gear whihc is most likely to have failed. The part from the dealer is the whole mechanism at about £250 ($350 or so I guess).
There are guides for removal you will find quite recently - MMI gears






