2008 R 2 Replication Errors

Hi experts
We are the admin of a 2008 R2 multi-site single domain and are facing some problems with replication. We also have an IPSEC tunnel over a WAN dividing the positions all on divide subsets.
In the mid position, there are two domain controllers (DC1 & DC2) and they can repeat very well. When I make StoreDC1, it was made in the mid position and was repeating fine.
When it was shifted to site, the forwarders were set up properly, the inferior DNS was place to DC1 and DNS on both sides decides the new, right IP addresses. I cannot prove if there has been any outbound duplication since the server was got online on site, but I can prove that there has been a few inbound.
The difficulty seemed to happen with the number of time the tunnel was downward before the servers were contacting each other. It was about two months.
Something that places out to me is the error message I find when UNC browsing to DC1 from StoreDC1. I find "Logon Failure: The target account name is incorrect". UNC browsing to StoreDC1 from DC1 works well.
From DC1, when running Repadmin; it confirms no fails to the replication associates. When you try to run the similar command from StoreDC1, you will get "Experienced the following operational errors trying to retrieve replication information:
8341 – DC1.Domain.local
8341 – DC2.Domain.local"
When I am running Repadmin /showrepl *, I find the same error messages from both DC1 and StoreDC "The target principal name is incorrect" and "***WARNING: KCC could not add this REPLICA LINK due to error".
Please give me a solution. Thanks in advance.
