Troubleshooting client driven pst-migrations - Only 5 of 15 migrating

I am running into some issues doing a client driven pst-migration. Currently only 5 files are in status migrating even though we configured 15 concurrent migrations in the task. In addition to that migration of the 5 seems to be stuck as the clients are not available / Outlook is no started.

-Holding and temp folder have a lot of space left and are both local

-Over 100 pst-files are in status ready to copy (from different mailboxes than the ones migrating currently)

In the past the column ClientMigrationStatus of the pstfile table helped troubleshooting but an old vox entry containing the meaning of the status (https://vox.veritas.com/t5/Ideas/Custom-PST-migration-reports/idi-p/799490 is no longer available. Does anyone have access to a list?

EV 11.0.1 CHF5. Over 500 pst-files already migrated

I appreciate any feedback. 

Regards

Marc