I don't see a problem. Sometimes, when users set the end action of the main menu to itself it has produced results similar to yours. Normally the end action of a menu is set to "stop," since it runs forever and does not reach its end action. You do have end actions on your submenus, and they appear to go back to the main menu. You may intend this. But I don't see a button on the submenus that goes back to the main menu.
Just as a test, I would change the submenus to "stop."
The more likely problem is that your intro appears to be chapter one of your main timeline. You could try adding a single asset/single asset timeline and use that for the intro. See if that removes the problem.