Carousel source: custom taxonomy not working

I’m trying to use a custom taxonomy as source for a carousel shortcode, but can’t make it work.

If I use a common post category, it works, it gets the featured image perfectly. If I use a custom post type’s custom taxonomy, it doesn’t.

I even tried using a custom taxonomy for media, with MCM plugin, with no luck. SU shortcode generator finds the taxonomy and the term but says “images not found”.

https://ww.wp.xz.cn/plugins/shortcodes-ultimate/