[Fermé] Wrong language category name in URL

Background of the issue:
I am trying to have consistent URLs for my website. I noticed an issue with the language category name in the URL. Here is the link to a page where the issue can be seen: lien caché.

Symptoms:
Instead of the expected consistent URL, sometimes the URL in English (second language) changes unexpectedly from lien caché to lien caché. The category name in the URL is being used from the default Dutch (NL) language.

Updating the NL products in bulk, with no changes, fixes the issue somehow. But this needs to stop happening, this hurts my shop.

Questions:
How does this happen?
How to permanently fix this?