[Fechado] 404 error for Echo Knowledge base articles in NL language

Background of the issue:
I am trying to resolve a 404 error issue with Echo Knowledge Base articles in the Dutch (NL) language on my site. My site has been live for years without configuration changes to Echo or WPML, except for plugin updates. Both plugins are on the latest version. The issue can be seen on this page: link oculto. The main support guide page works correctly: link oculto.

Symptoms:
I am experiencing 404 errors for Dutch language articles, even though they used to work correctly. The language switcher works for all languages except Dutch. This issue affects all Echo KB articles and categories. A similar example for categories is here: link oculto.

Questions:
Why are the Dutch language articles causing 404 errors?
How can I fix the 404 errors for the Dutch language articles?