Why do I need to clear current data from the Target Store in order to restart migration?
Usually, restart migration means that something is wrong with the data on a Target Store. It can be influenced by 3rd party extensions, inappropriate development, bugs during shopping cart installation, etc. That is why launching a new migration (remigration) to a store, filled with corrupted or modified data, is not recommended since there is a risk of mixing/duplicating data. In order to avoid this you will need to clear current data from a Target Store before migration. In this case all the corrupted/modified data will be deleted. Your Source data will be moved to a clear Target Store, preserving relationships between entities.
Please note! Clearing data from a Target Store is irreversible option, so we highly recommend to make a backup before restarting the migration.