Snapmirror Incremental Transfer failing

Hi,

snapmirror incremantal transfer is failing and giving   Last Transfer Error: Failed to start transfer for Snapshot copy "snapmirror.3646c8de-de56-11e6-adaf-00a098642514_2154793469.2017-02-04_180345". (Failed to start transfer. (Duplicate transfer specified (Replication engine error))).

Any ideas ?

Thanks,

Tuncay