Hi there,
Thanks for updating the thread! There is actually a bug that should be resolved in the next Cornerstone update. The div part in the JS is being cleared for some reason. You will need to reapply the original code we provided back into your Cornerstone Custom JS after updating to the next update.
In the meantime you can add this under Custom > Javascript in the Customizer.
jQuery(function($){
$( ".page-id-6713 #x-section-1" ).wrapInner( "<div class='section-overlay'></div>" );
});
Hope this helps – thanks!