I think I found it - somehow the wp_header is after opening body tag instead of just before closing head tag.
I’ll fix that but can’t do it now because I (as mentioned elsewhere) do not have server access. I’ll be able to look at this after Wednesday.
The ShortCodes are in the preview because there are description meta tags, and there is no content in that page but the shortcodes, and these tags are populated with excerpts unless specified else, and excerpts do not expand shortcodes, and are built with whatever is first in the cotnent.
Thus it is how it shows in the meta tags.
As you can see on the other pages it does not happen. That is because those other pages have content prior to the shortcodes. This is also a reason why I asked for a short intro to this page
However of course, I am happy to actually install SEO Plugins or do a more advanced SEO handling in the theme (as of now, it is simply how WP DevHub handles it.