Hello there,
I was just working on a new menu for my site in the header builder and I discovered that when I insert a DIV element and set its tag to <a>, it prints on the front end the containing elements as siblings to the div and not as children of the div. It works as expected in the Cornerstone builder. The reason I know it is a bug is because when I change the “tag” of the DIV element back to <div>, it works as expected in the front end.
I can explain further, if necessary, but I’m in a time crunch with other things at the moment. In the meantime, you can see the link above in the “Resources” mega menu for an example.