On our current megaproject we had a problem where during STC (save to central) user A would need an editing request from user B. User B would need to STC to give the element(s) to user A, but as part of that, user B needed an element from user A, which required user A to STC themselves...
So neither person could save, unless one person gave up their work!
It turns out the problem relates to corner mullions forgetting which wall they're associated with. The workaround is to swap out all corner mullions for regular mullions; we have placeholder mullion types so we can right click the type in the Project Browser and swap them all back.
Revit Support is working on a fix for this bug now, which affects Revit 7.0 and presumably Revit 8.0 up to and including the May 23rd build.