This article explains about the problem when opening a Group Policy in a forest where you have more than 1 or more domain controllers and running on a different sites.
When you open up Active Directory Users and Computers > Right Click an OU > Property > Go to Group Policy Tab and Open the GPMC or Edit Group Policy > then again you right click on a Policy and click on Edit > then snap-in will open the policy but it will open on a very distant server.
You will see something like that:
Policy Name [name of the distant server]
This happens because when you open a GPO it contacts the Domain Controller for editing GPO according to the settings configured in GPO. By default it contacts PDC Emulator to avoid the collisions in FRS.
To resolve this you can set a policy setting in GPO:
If multiple administrators manage a common GPO, all administrators should use the same domain controller when editing a particular GPO in order to avoid collisions in the File Replication service (FRS).
Use the Change Domain Controller function to specify the domain controller to be used for a given domain or for all sites in a forest. In each case, you have four options:
•The domain controller with the Operations Master token for the PDC emulator (the default option)
•Any available domain controller
•Any available domain controller running Windows Server 2003 or later.
•This domain controller: Select a specific domain controller to be used.
Group Policy: Change Domain Controller Selection: