The dev of the plugin couldn’t find any issue, he suggested to try another shortcode from other plugins to isolate the issue and I did.
I created a couple of posts and inserted as a content only the shortcodes from two plugins
Plugin “WP Sitemap Page” shortcode [wp_sitemap_page only=”post”]
both shortcodes only insert some html code and both plugins are not processed in the excerpt
Can this help in any way?