Healthcare.gov's mobile header is mobile

On my Android phone, the Healthcare.gov mobile site's header doesn't always stay put at the top of the screen. It slides up and down the screen as I scroll up and down the page -- sometimes completely disappearing.

Once the mobile header goes mobile, tapping the menu button, the language button, or the Log In button does nothing. However, those options are available if one taps the location where the header should be displayed.  The header display moves but not the tap location to activate the buttons.