If you added a DC and accidentally (or simply forgot) to change the name of the computer. Here is how to do it correctly, run these commands using PowerShell:
netdom computername CURRENTNAME.mydomain.local /add:NEWNAME.mydomain.local
netdom computername CURRENTNAME.mydomain.local /makeprimary:NEWNAME.mydomain.local
Then after reboot:
netdom computername server.ckmay.local /remove:CURRENTNAME.mydomain.local