weird menu issue

Hi guys, before i start id like to say i love the no8 theme, its totally perfect for what I’m using it for.

https://www.sawyerandsawyer.uk

when you goto the site and start scrolling the menu will shrink to grey bar with the menu items in white which is what it should do but what I’m finding is after i have been in to a portfolio item such as Acklam Grange Transition Brochure the men stops resizing and just stays transparent with white menu items. hope that makes sense, i go back to pages that it was working ok on and it does the same thing. not sure whats going on perhaps something is being cached after being on portfolio items, it works again if i clear my history, CMD+R doesn’t rectify, have to totally clear my history.

Thanks in advance. hopefully the issue will occur for you so you can see what the problem is. cheers