Cyrillic page’s slug bug

Hello,

I’m from Bulgaria and we use Cyrillic alphabet.

For good presenting and SEO I use Cyrillic slug for my post and pages, but there is some problem with cyrillic page’s slug.

The bug come when I change the Permalink Structure to “/%category%/%postname%/”.

For me that is perfect structure, it work like that:
For pages:
“https://www.example.com/first-level-page/second-level-page/last-page”
For posts:
“https://www.example.com/category/sub-category/post”

But when I put Cyrillic in my pages’s slug it go to 404 error page in my blog. There is no sense how or where I use it in my pages (page’s only!).

https://www.example.com/about-us – work
https://www.example.com/за-нас – don’t work

Real test:
https://www.misli.de/devblog/за-нас/ – don’t work
https://www.misli.de/devblog/?p=2 – the real address