Open Migrator question

I am using OpenMigrator/LM for Windows to migrate a couple of large volumes.  I've tested the OM on a different machine with small volumes before proceeding and it appears it worked perfectly well.  Once the migration was completed it starts to show "Insync" state and I am able to select "Complete migration" when I am ready for cutover.

So fast forward to production data migration and after one of the large (3TB+) volumes finished instead of showing "Insync" it is now showing "Source and destination volumes are not identical" and migration state "Ready".  This is not what I was expecting to see.  And the migration was not really complete because it did not switch over to the target volume nor changed the drive letter over to the new volume. Well, it was not supposed to happen automatically anyway. 

My understanding was and that's what the manual says.  Writes go to both volumes during migration and are kept in sync until you manually select "Complete Migration" option.

So does this mean I have to redo this again?  How do I make sure it stays in sync after data copy is complete?