More than three subforums?

When I add more than three subforums, one of them disappears from the list both in the control panel and on the forum page, even though the forum is still accessible by URL and all the posts are still there. When I deleted the new subforum, the one that disappeared became listed again and everything.

That's very strange; there's no reason that should happen. Can you link me the game; I'll take a look? Anyone else face this issue?

Link here

I deleted the fourth subforum though.

Here, I've added a fourth subforum again. Delete it (if you can?) and see that the forum it bumped reappears in the list, not missing any posts are anything. https://gamersplane.com/forums/3987/

The disappearing subforum can still be reached via link.

This is happening to me, too.

Here.