My bad; I surf with NoScript and forgot to activate JS when testing. Too early for me, I'm afraid ;-)
The mobile menu is implemented with JavaScript, using
/wp-content/themes/swank/lib/js/responsive-menu.js, which relies on jquery (/wp-includes/js/jquery/jquery.js). So try excluding those (add "responsive-menu.js, jquery.js" without the quotes to the comma-seperated list of JS optimiztion exclusions?
frank