Ever since I did a setup:upgrade I've been having some issues with the Admin not doing what it's supposed to do, particularly on the Catalog > Categories section.
As you can see, on the backend I'm not including it on the menu.
But it still shows up regardless.
I'm able to remove the other categories (although sometimes, for some reason, all of them except Default get removed and it's hard to get them back) but no matter what I do the Default category won't go away.
