Hello.
I had a similar problem, shortcodes were displayed in the slider.
Change.
/templates/designs/design-4.php Line 38
$excerpt = strip_tags(get_the_content()); ?>
to
$excerpt = mb_strimwidth (strip_shortcodes (strip_tags(get_the_content())), 0, 260, ‘ ‘); ?>
maybe not the best solution but it worked for me.
