just reporting a misbehavior from other plugin, which is not available anymore (oqey-gallery)...
at Admin level, the menu of the plugin works just fine
but at Editor level it wasn't going to the proper page, 404 instead
i found that the other plugin was adding its menus and submenus without using a slug, it was using __FILE__ in the add_menu_page and add_submenu_page
maybe this can happen with other plugins too