We use WPML for "Use different slugs in different languages for Books." So in English we have urls like /en/books/abc, in Dutch /nl/boek/abc and in French /fr/livre/abc. All Dutch book urls are fine, but all book urls in EN/FR give a 404 Page not found.
However for issue that are caused by translation it would be best to open a ticket with our WPML team as well, as they are better trained to handle these issues.
I see in the upper left corner ...itinerainst/, what url is that? You'll need hidden link like in my original post at the top and hidden link for the admin.
What was it set to before? And why did it work before and then stopped working until you just now changed that setting?
Because the CPT Article is set to "Use the normal WordPress URL logic" (screenshot 4) and those translations work perfectly. We have /nl/artikel and /fr/article/ and that just works.