Never mind. I just deleted the demo and built the site from scratch. Have had no issues.
Perhaps the One Page Restaurant Demo is corrupt?

No. It is literally anywhere in the site.
Whenever I try to add any element – a layout element or a content element – it crashes the whole section I’m working on. For example, in the menu portion of the site, If I add say a new color section and then preview changes, most if not all of the menu disappears. I then have to back up a step for the menu to reappear. This should only take me a few hours to complete but I’ve already spent most of a day workign on it.

I have tried using Google Chrome, Safari and FireFox browsers to see if that makes a difference but it does not.