Mega Menu issues after WP and theme updates

My Mega Menu used to align to the left of the entire navigation bar, and since updating WP and the Enfold theme it now aligns to the parent tab causing one of the columns to move outside of the browser:
http://www.bhutantravelbureau.com (Tours & Treks tab)

I have looked at the new header options and cannot see anyway to correct this, and the removing the custom CSS that applies to the mega menu as below has no impact:
#top #header .avia_mega_div > .sub-menu > li > ul > li a {
padding-left: 8px;
padding-right: 5px;
}

#top .header_color .main_menu .menu .avia_mega_div ul .current-menu-item > a {background-color: #e1e1e1;}

#header .avia_mega_div .units {
padding-left: 8px;
padding-right: 8px;
}

#top .main_menu .menu > li:last-child > a {padding-right: 13px;}

#top #header .mega_menu_title a {font-size: 15px !important;}

.avia_mega_div .avia-bullet {margin-top: 10px;}

A fix for this would be much appreciated.