Not related to the update, I think (I vaguely remember it in the past, but forgot about it):
When you go to an invalid link such as http://demo.themesandco.com/ab, you get a 404 error and a helpful search form. When you go to a second-level invalid link (e.g. http://demo.themesandco.com/ab/cd you get the same, single search form.
When you go to a third-level (or deeper) invalid link (e.g. http://demo.themesandco.com/ab/cd/ef you get two search forms.
@Nikeo: any idea why?