[Samba] Samba 4.4.2 AD DC demote fails

[Miguel Medalha]

Demotion of a AD DC fails with the following errors:

If I explicitly select a partner server with the "--server=" option the 
error is:

Deactivating inbound replication
Asking partner server [selectedDC] to synchronize from us
Error while demoting, re-enabling inbound replication
ERROR(<type 'exceptions.UnboundLocalError'>): uncaught exception - local 
variable 'e' referenced before assignment
   File 
"/usr/local/samba/lib64/python2.7/site-packages/samba/netcmd/__init__.py", 
line 175, in _run
     return self.run(*args, **kwargs)
   File 
"/usr/local/samba/lib64/python2.7/site-packages/samba/netcmd/domain.py", 
line 797, in run
     raise CommandError("Error while sending a DsReplicaSync for partion 
%s" % str(part), e)


If I don't explicitly select a partner server, the error is:

Deactivating inbound replication
Asking partner server [someDC] to synchronize from us
Error while demoting, re-enabling inbound replication
ERROR(<type 'exceptions.RuntimeError'>): Error while sending a 
DsReplicaSync for partion DC=lan,DC=cimbal,DC=pt - (8440, 
'WERR_DS_DRA_BAD_NC')
   File 
"/usr/local/samba/lib64/python2.7/site-packages/samba/netcmd/domain.py", 
line 786, in run
     drsuapiBind.DsReplicaSync(drsuapi_handle, 1, req1)


I have two other DCs which seem to be working correctly. Replication and 
name resolution are working. All 7 FSMO roles have been successfully 
transferred to one of the other DCs prior to the demotion attempt.

Can anyone here point me to the right direction? I would like to avoid 
brute force removal of the DC by "--remove-other-dead-server".