[Samba] Samba on Debian 8; NT4 domain, win10

[Stefan G. Weichinger]

I am doing another classic-upgrade for another customer.

I get:

Importing groups
Could not add group name=Domain Admins ((68, "samldb: Account name
(sAMAccountName) 'Domain Admins' already in use!"))
Could not modify AD idmap entry for
sid=S-1-5-21-2777655458-4002997014-749295002-1006, id=0,
type=ID_TYPE_GID ((32, "Base-DN
'<SID=S-1-5-21-2777655458-4002997014-749295002-1006>' not found"))
Could not add posix attrs for AD entry for
sid=S-1-5-21-2777655458-4002997014-749295002-1006, ((32, "Base-DN
'<SID=S-1-5-21-2777655458-4002997014-749295002-1006>' not found"))
Could not add group name=Domain Guests ((68, "samldb: Account name
(sAMAccountName) 'Domain Guests' already in use!"))
Could not modify AD idmap entry for
sid=S-1-5-21-2777655458-4002997014-749295002-1008, id=65534,
type=ID_TYPE_GID ((32, "Base-DN
'<SID=S-1-5-21-2777655458-4002997014-749295002-1008>' not found"))
Could not add posix attrs for AD entry for
sid=S-1-5-21-2777655458-4002997014-749295002-1008, ((32, "Base-DN
'<SID=S-1-5-21-2777655458-4002997014-749295002-1008>' not found"))
Could not add group name=Domain Users ((68, "samldb: Account name
(sAMAccountName) 'Domain Users' already in use!"))
Could not modify AD idmap entry for
sid=S-1-5-21-2777655458-4002997014-749295002-1007, id=100,
type=ID_TYPE_GID ((32, "Base-DN
'<SID=S-1-5-21-2777655458-4002997014-749295002-1007>' not found"))
Could not add posix attrs for AD entry for
sid=S-1-5-21-2777655458-4002997014-749295002-1007, ((32, "Base-DN
'<SID=S-1-5-21-2777655458-4002997014-749295002-1007>' not found"))
Committing 'add groups' transaction to disk


-- why "already in use" ?