Hello,
 
Migration Batch status is showing “SyncedWithErrors”, what should I do?
Migration Batch status is showing “SyncedWithErrors” and few mailboxes are synced and failed in the batch. 

Kindly first check the exact failure reason from ECP under Migration section. If this is something related to missing SMTP on target exchange or Large item limit exceeded then kindly solve it at your end. Once you have solved the case at your end, you can simply restart the batch from Efflux Migrator by click on “Restart Batch” button.