Initial Sync Failed

My Realm apps keep getting “initial sync failed” errors. After deleting __realm_sync and creating new apps, they are still failing. The chat support could not solve this and suggested I ask for help here.
What could cause this failure, and how can I solve this?


initial sync failed: initial sync worker for ns=‘duet.File’ stopped with error: failed to insert change into history during initial sync of ns=‘duet.File’ after copying 0 documents: failed to execute batch upload integration during initial sync: error performing database transaction to flush translator batch: inserting entries into client history failed: connection([-519598]) incomplete read of message header: context deadline exceeded


Error syncing MongoDB write