mail tagging into folder not working

pingus01

Several mailboxes have been migrated from iredmail to mailcow with imapsync. Some of the mailboxes do not sort tagged mails (+ sign) into subfolder while others do. Tagging into subfolders is activated.

I also tried to add the tagging part of the global filter into a sieve filter inside the mailbox. Still not working.

Any idea what I can check to solve this problem? Is it a flag in the database?

Thanks
Pingus01