I had the same issue. Looks like the appropriate class is not being added to the body tag. I’m not sure if this is totally off base but my hack that seems to be working is:
At around line 353 – “Extend the default WordPress body classes.” I added the following:
if ( is_page_template( 'page-templates/full-width.php' ))
$classes[] = 'no-sidebars';
