man smb.conf version 3.0.2:
" Please note that setting this parameter to + causes problems
with group membership at least on glibc systems, as the charac-
ter + is used as a special character for NIS in /etc/group.
However in example configuration the winbind separator through Samba HOWTO Collection is routinely used as '+'.
Fixed in SVN. Thanks !
sorry for the same, cleaning up the database to prevent unecessary reopens of bugs.