Mega menu headings

Hi guys,

I’m struggling to work out why the headings in my mega menu aren’t linking to their relevant pages. Instead, when you click on the heading, the sub menu disappears and reappears.

I’ve included the website link. If you hover over the Services heading in the main menu and then try clicking one of the four main headings you’ll see what I mean.

Any help would be greatly appreciated.

Many thanks,

David.