This behavior is by design.
When creating a new EV server to take over archiving from an old EV server, it is recommended to disable the archives on the old EV server prior to enabling them on the new EV server. This is to prevent a situation in which a mailbox is associated with two different archives. The Move Archive feature enforces this recommendation.
In situations where it is not possible to disable the archives prior to moving them, then the administrator must perform the move by exporting the old server's archive to PST and import them to the new server, rather than using the Move Archive feature.