VBulletin automatically copying new threads as new threads

Apologies if I misposted this thread, but I have a problem that vBulletin seems to be automatically reposting new threads in another forum.

The new threads have identical topic titles and show the first 1 or 2 lines of the original forum post with a 'read more' link to the original post.

The new posts are made under my user account.

What could cause this behavior? I have disabled pingbacks. It seems this is some sort of built-in behavior, since it's been an issue since I did maintenance 2 weeks ago. I have however no idea what it is I have done, that could have caused this.

(I will not post links for example purpose, as this might be considered spammy)