I did some tests..
on an old VM with SME 9.1 and samba-3.6.23-24.el6_7.x86_64 I enabled the domain controller feature, joined a virtual w2003 machine, logged successfully with 2 users..
I then updated SME and now I have samba-3.6.23-35.el6_8.x86_64
I'm still able to login with the users I tested before and with some other users..
IMO this seems resolved
Dani: should we update bug 9448?