When I use the header image, the menu bar is working strangely, that is not stretched to the full width of the screen. But when I scroll down the page, and when the image header becomes is no visible, then the menu bar stretches the entire width of the screen.
I tried the automatic crop the image, tried without crop (in original size, wider than the screen), but the problem is the same.
See an example here
Tell me, please, how to get around this strange behavior of the menu bar?