I have the following scenario:
I had a unknown name service record in my company DNS Forward lookup zone under the _msdcs (greyed out) folder. The record was in a unknown computer name format. I have attached the DCdiag results while the the rouge entry was present. During this time computers started giving problems with logging on. PC's where taking too long to present the user with the logon screen. I have attached log files with error codes recorded on the PC's in the event logs.
After i removed the entry, PC's seemed to be fine but this was only temporary as more users started to complain. I did some more research and discovered i was not supposed to delete the rouge entry but rather point it to the correct GC on our LAN. I did this and tested again, this seems to have solved the issue. I am still however getting calls from users who are complaining about slow PC's at logon and these PCs are complaining about DNS and GPOs in their event logs.
I have substituted the actual server name in the files as follows:
Actual DC name = Servername
Actual Domain name = Domainname