This incident has been resolved.

The issue with on premise syncs should also be fixed now.
If you still have issues with your sync, please contact support and we'll have a look.

We're still monitoring the situation for other issues caused by the database migration of this night.

We're facing problems with some on premise synchronisations. This issue caused by the database migration of last night. We're mitigating this specific issue and looking into similar issues caused by the database migration.