When changing the default group for a user through ADUC, an error is returned to the user and following opening of the group tab show the default group twice.
This problem is due to the fact that in the LDB files, user has his primary group changed but he as still a member-of attribute related to the group that is now primary.
I think the version numbers for SAMBA 4 Alpha/TP aren't worth to keep since we don't support any versions longer yet. Because all bugs filed will be propagated from version to version until they are fixed (for now at least) this field isn't necessary yet.
Should also be fixed now in "master".