Twitch with Dropdown Menu

Hey everyone, we have been working on our website and came across one big problem. The dropdown menu bars under “about” and “services” have a twitch. It is much more visible under the “about” menu option. We are unsure what is causing it, or how to fix it. The website is:

http://dev.progressivemediaconcepts.com

It happens occasionally under the “services” drop down. I’m assuming that it is a glitch with the theme, but wondering if anyone has any fixes? Theme is Luxury.

Thanks!