You can restart the netlogon service & it should refresh all the records in dns & create the missing records like cname, srv etc.
You can recreate the missing cname manually & GUID of DC can be used from AD sites & service, click the site, server,server name, right click Ntds settings you will see the GUID name & create it.
If, you have two _msdcs folder listed in dns, delete the greyed one & even if you delete both & restarting netlogon & dns server service will recreate _msdcs folder followed by dcdiag /fix & netdiag /fix.
You can also use ipconfig /flushdns & ipconfig /registerdns
Um einen ausführlichen Test der AD DNS Dienste auszuführen:
dcdiag.exe /test:dns ausführen. Dies dauert für gewöhnlich dann ein paar Minuten.