Issue with menue overlay

Hi,

I like the "Box"-Template very much! Good work! But I have a problem with the overlay of the main menu. In the demo it has a transparency-effect on the header-picture.

In my project I have also header-pictures and the menu is not transparent. That is okay that way, but if I click on another menu-title and the new page is loading, there is a strange transparency-effect in the menu just for a second. The main menu flickers to gray (the menu-color is white) and the picture scrolls up a bit. Shortly after, everything is okay again.
I can´t find the solution myself... Could you please help?
Thank you in advance.

Hi

Please tell me the url to the exact page with an example of this issue.