Random Horizontal Rule undre submenu

Since a recent theme update, we are experiencing an obnoxious (and very short) horizontal rule under sub-menu captions (within mega menu). I have looked everywhere and can’t seem to find which css is causing this.

Also, these captions or headings now appear as menu items when I roll over them. They did not do this before the update.

The list of mega menu css classes in your documentation doesn’t seem to provide every style I might possibly need.