Menu not showing correctly with 4.0

I think it was since WordPress 4.0 was installed that this problem appeared.
On my site, https://www.cadagency.co.uk the menu is displaying incorrectly.
On the Admin side the menu “header” is selected as the main-menu but it is showing the “footer” menu on the site as the main-menu
This has only just started happening.
I have tried to unselected the menu and reselect it but its just not doing anything.
The “footer” menu is actually being used on my mobile site as the main menu but I can’t work out whats wrong with the main site now