WordPress Admin Menu defining function is seperate file

The $function argument of add_menu_page should be a function that produces your page output, or if omitted, then the $menu_slug argument can be a file that when included will output the menu page.

But your output right now has nothing to do with the add_menu_page call, the problem is that you’re requiring aio_dashboard.php, which has a function hooked to current_screen. The current_screen action should not generate output, that’s not what it’s for, it fires too early in the load process. Its purpose is for adding filters and actions based on the current admin page being viewed.

Change the add_menu_page $function argument to contain the function that outputs the page content, remove the add_action call hooking that function to current_screen.