"Read more"-link points to "Home"

Hello!
I have a slight problem on my homepage and I have no idea what the issue could be – so I really hope you guys here can put some light in my darkness ??

I’m using the “List Category Posts”-PlugIn on my site to display the last posts to a category. So I put the [catlist name=”xxx”] in the excerpt of a page and added the following to the functions.php:

add_filter('the_excerpt', 'shortcode_unautop');
add_filter('the_excerpt', 'do_shortcode');

That worked. The weird thing is:
If I put “[catlist…” in the excerpt, the “Read more”-link points to the Home-page. If I delete that line (and no posts are shown), then the “Read more”-link works.

You can try it out at https://www.wurmweb.at, directly on the Home-page (“mehr lesen” in german).

I would be glad if somebody has any idea ??
Thanks a lot,
Manuel