Yesterday when I tried to change my mailadresse for several forum accounts on one server it was NOT working on my server with the latest stable release, but it worked on the one with the current developer build.
I am not sure if the #Friendica versions matters at all.

What could be the reason? Has it to do with the kind of delegation, I might have the old delegation on one server (same mail and password) and the new delegation via the backend settings.

!Friendica Support