Unable to migrate mailboxes after upgrading to CU8

server 1: Version 15.0 (Build 1076.9)
server 2: Version 15.0 (Build 847.32)

Im trying to  some mailboxes from "server 1" to "server 2"  that are taking up allot of resources , but after upgrading from CU4 to CU8 on server 1 I get this error message:

MapiExceptionMdbOffline: Unable to get mailbox information. (hr=0x80004005, ec=1142)
Diagnostic context:
    Lid: 65256
    Lid: 37815
    Lid: 41911   StoreEc: 0x476
    Lid: 1494    ---- Remote Context Beg ----
    Lid: 39576   StoreEc: 0x977
    Lid: 49696   StoreEc: 0x476
    Lid: 1750    ---- Remote Context End ----
    Lid: 50103
    Lid: 48311   StoreEc: 0x476
    Lid: 43959
    Lid: 60343   StoreEc: 0x476+ CategoryInfo          : NotSpecified: (:) [New-MoveRequest], RemoteTransientException+ FullyQualifiedErrorId : [Server=server2,RequestId=324ce0ea-83a1-456a-a559-4577a7ee2c73,TimeStamp=05.05.2015 16:27:4
   4] [FailureCategory=Cmdlet-RemoteTransientException] B799AEC5,Microsoft.Exchange.Management.RecipientTasks.NewMove
  Request