Gitlab integration with YouTrack doesn't work for merge requests

we just startet to use YouTrack as new issue tracking tool and connected it with gitlab.
For the commits page everything works just fine, the ticket-id in the header refers to the youtrack issue.
But on the merge request page the link still refers to jira (we used jira before, but disabled it everywhere).
How can it still have the jira link, even if we disabled this integration?

Thank you in advance!
Best regards,