DAG - Copy Status - Service Down

Odd problem on a soon to be production 2010 DAG environment.

3 node DAG, 2 in primary site on same subnet, 1 in DR site. No dedicated replication network as yet.

When looking at database copy status in EMC I see copy status as Mounted or Healthy for the node I am on but both other nodes are listed as Service Down. It can also take a LONG time for the status to be displayed.

If I run Test-ReplicationHealth for the local node it checks out perfectly.

If I run it with Test-ReplicationHealth -Identity OtherNode I get the following:-

RunspaceId       : 616aa378-5951-4393-b660-f0c6860b7ccc
Server           : GLA-EXMB-01
Check            : ActiveManager
CheckDescription : Checks that Active Manager is running and has a valid role.
Result           : *FAILED*
Error            : An error occurred while communicating with the Microsoft Exchange Replication service on server 'GLA
                   -EXMB-01'. Database operations such as mounting, dismounting, and the ability to have failovers or s
                   witchovers may not be available. Verify that the Microsoft Exchange Replication service is running a
                   nd review the Event logs for more details. Error: An Active Manager operation failed. Error: Operati
                   on failed with message: Error 0x71a (The remote procedure call was cancelled) from cli_AmGetActiveMa
                   nagerRole.

and

RunspaceId       : 616aa378-5951-4393-b660-f0c6860b7ccc
Server           : GLA-EXMB-01
Check            : TasksRpcListener
CheckDescription : Checks that the Tasks RPC Listener is running and is responding to remote requests.
Result           : *FAILED*
Error            : An error occurred while communicating with the Microsoft Exchange Replication service to test the he
                   alth of the Tasks RPC Listener on server 'GLA-EXMB-01'. Verify that the Microsoft Exchange Replicati
                   on service is running. Error: A server-side administrative operation has failed. The Microsoft Excha
                   nge Replication service may not be running on server GLA-EXMB-01. Specific RPC error message: Error
                   0x71a (The remote procedure call was cancelled) from cli_GetCopyStatusEx2.

If I suspend the copy then resume it will usually re-appear but will then fail again later on. Although half the time it will fail to suspend the copy since it says it can't contact the remote node.

Makes me somewhat unconfident about auto-failover.

There have been no changes to the AD environment but we have just installed a similar set of Exchange servers in a completely different site over a slow WAN link.

Anybody got any thoughts?

Thanks

Neill