Hi,
I have done some tests and can confirm that the method
$post_id = 9865;
$shortcode = '[mbv id="' . $post_id . '"]';
echo do_shortcode( $shortcode );
Will work on a full page refresh but not if the page is loaded via an ajax method
Also, I have tested this with other shortcodes in my system using the "echo do_shortcode( $shortcode );" method and they load all via ajax as without problem
Any ideas?