AD Replication Error 1908 (Source DSA)

Hi all,

I’m troubleshooting an Active Directory replication issue (error 1908 – “Could not find the domain controller”) in a multi-site environment with 16 domain controllers across multiple locations.

The problematic Domain Controller (Site A-DC) is displaying a 6% failure in the replication summary with the 1908 error code in the Source DSA but the Destination DSA do not display any errors. If I replsummary in other DCs, I will see the same result. However, If I run the showrepl command, the result displays all successful replications with no errors. 

A-DC is used as a replication path and holds the FSMOs roles (Site A is the main DC) and I believe it is also affecting DFSR replication from Site A-FS server to the other file servers. A-FS uses A-DC as its logon server. 

The below is what I have verified:

•  I have verified that forward and reversed lookup zones have the correct DNS records (Checked SRV records _ldap._tcp.dc._msdcs, _kerberos._tcp, and IP addresses) 
• All the DCs resolve correctly A and PTR records
• nltest /dsgetdc:domain.com successfully returns domain controller
• Confirmed Secure channel to be true in A-FS
• Verified KDC is running in A-DC (I have not trying purging the KDC tickets yet but doubt this will resolve the issue)

Troubleshooting performed:

• flushed/re-registered DNS 
• Restarted netlogon services
• Time sync wouldn't have a play here since all the other DCs are syncing with A-DC.

Any guidance or similar experiences would be greatly appreciated.

Miguel