I can't use the word in url slug

I created a page, named “Reklam”

The url slug became “reklam” as expected. The preview page is full of white blank.

If I change the url slug like “reklama”, “reklam-vadsa” or sth like that it works very well.

I tried to check whole database If any other post or tag using same url slug; I didn’t find anything.

But I want to use “reklam” url, how can I solve the problem? Any suggestion?