I’ve just created my first for Pods UI plug-in, the code is below, more or less a copy of the MBN example. I’d expect from the add_object & add_submenu options, to get a main admin menu item of Caza Mayor and a single sub-menu of Cotos. What I actually see is two submenus – Caza Mayor and Cotos – the Cotos option works fine, I just don’t understand why the Caza mayor submenu is present.
I guess it’s not really a pods problem, rather a problem with my plugin code, but I’m not really where to check next.
Your sub-menu code is set to point at a different identifier than the parent one, so it sets up additional sub-menus automatically. This is WP core, so more information can be lifted from their documentation on add_object_page