@caovillanueva I actually found the issue in the meantime, but forgot to update this thread. I also found a workaround, but not a real solution.
I've reported the issue on GitHub: https://github.com/PrestaShop/PrestaShop/issues/23815
It got closed, but not really resolved. 🙃
TLDR: Turned out it was the slash ("/") symbol (and sometimes hyphen ("-")) that caused issues. Once I renamed categories and changed these symbols, it works well.
Could you try, if this is the issue on your end as well?