Responsive menu not displaying all items

Site: http://rtsidequest.com

The native WP menu has a number of items, with three levels. When the viewport is reduced to activate the plugin’s menu, a fair number of menu items are not included in the responsive menu.

Anyone have a similar problem? Wanted to check here before diving too deep into debugging.

Thanks!

http://wordpress.org/extend/plugins/responsive-select-menu/