On this page; Fearsome Face which is effectively a single post in a WordPress site, the menu collapses.
On pages other than a single post page, it seems to be OK: Home
The result is that the sparkly underline doesn’t show nor does the transparent .png on the <ul>
That you spotted it makes my think you are a minor deity. That you knew how to fix it and helped me is pushing you towards becoming the Fourth Member of the Trinity!