Issue: Page in categories-list

That page used to be a category, but the category behavior was unchecked in the editor "Treat this page as a: category"
Unchecking the box removed the behavior from the page, but it was still remembered to be a category and it was still possible to add pages to it. There was a similar problem when unchecking the box for books.

This is unusual because I remember fixing this not too long ago. Oh well. Marked as fixed in the next release. The upgrade script will reapply the behavior to these pages that are remembered as categories but don't act like them. After the upgrade unchecking the box again should work as expected.