You can delete the msdcs folder safely,restart dns server & netlogon service it will be created again.
Rename netlogon.dnb & netlogon.dns file,restart same service dns & netlogon,file will be recreated.
The msdcs folder will be shown inside root domain of your zone,expand & right click look for NS tab,if entry is not there,create it.
run dcdiag /test:dns & dcdiag /fix.