Mobile nav menu disappears when I scroll

When I view my site on a mobile phone and click on the hamburger/menu icon, the navigation expands. The list is long enough that to see the full list of links, I need to scroll down. When I try to scroll down though, the expanded menu disappears.

I found that if I disable this code in main.js,

$(window).resize(function(){
$(‘.lq-mobile-drawer-header’).hide();
});

it works properly (allows me to scroll without collapsing the menu), however a new problem occurs.

When I disable this code, the page header <section class=”page-title-bar”>, no longer sizes the way it’s supposed to. The width is not calculated properly and it leaves a margin on the right side where there should not be any.

Please help, thank you!

The page I need help with: [log in to see the link]