I had the same problem. While we wait for the devs to update their plugin you can apply this fix.
In shortcodes-ultimate\assets\generator.js line 20.
Change this line :
window.su_generator_target = $(this).data('target');
to
window.su_generator_target = $(this).parent().parent().next().find('textarea').eq(0).attr('id');
Hope it helps. Works for me. I am using the latest version of WP and plugins.
Colsie