Sorry for not giving you complete information from the beginning. It’s not just the menu that jumps, when you click on a link and the new page is loaded it moves a little bit sideways. I think this problem is related to the length of the page and when the scroll handles are activated. I first saw it when I tested the site on a mobile device where the scrolling handles wasn’t visible and thought it had to do with the mobile menu.
Do you think it’s possible to get rid of that shaking or movement?
Will you take a look for yourself? http://redhousepr.com