0xc000006a means the username or password is incorrect. Since this is a computer account, this usually means that the password is incorrect.
How to use Netdom.exe to reset machine account passwords of a Windows Server domain controller
FYI - restoring old domain controller backups can have several unwanted side effects. One is referred to as "lingering objects". This is when an object that was removed is re-introduced into the replica from a domain controller that did not receive the removal replication.
See the following for detailed information on dealing with lingering objects.
Server 2008 DC rejecting replication requests