This is partially a duplicate of this question, so I don’t see any reason to retype all the info.
The previous issue created for that question, UE-44570, is marked as fixed, so I am assuming there has been a regression at some point since that fix.
The difference now is that the whole GUID is not updating, while before, part of the GUID would update. It also appears that if I mark the property as EditAnywhere, it sometimes is not editable in the editor after I have changed it from C++.