Routes of taxonomies in other language mode, sometimes work, sometimes don't work ...

I have a taxonomy called "Product -Groups", works like categories concept.

The slug used to navigate to these groups (the one in routes.yaml) is: taxonomies: product-group: nl: 'producten/{slug}' en: 'products/{slug}' fr: 'produits/{slug}'

The slug works in the default language (NL), but sometimes fails for other languages. Some taxonomy terms are accessible in EN and FR, and some just throw a 404.

Some cases it is fixed when I delete the cache folder and re-save some entries. Though this is not a guaranteed solution, sometimes it is not fixable at all. Very annoying.

I expect this to be basic functionality. What am I doing wrong? What can I look into a bit more?

Can't get any response on github issues. I'd really love some help ...