Problems with %Encoding in Non-English URLs

Hello everyone,

I’m creating permalinks for posts in Korean on my WordPress website, and I’m having an issue with %encoding in uppercase and lowercase.

When I copy the following post URL from the address bar in Chrome, it is copied in uppercase:<font _mstmutation=”1″></font><font _mstmutation=”1″></font><font _mstmutation=”1″></font>

https://vietnamguide.co.kr/???-????-??-??-??-???/
https://vietnamguide.co.kr/%ED%98%B8%EC%B9%98%EB%AF%BC-%EA%B3%B5%ED%95%AD%EC%97%90%EC%84%9C-%EC%8B%9C%EB%82%B4-%EB%B0%A9%EB%AC%B8-%EB%B0%A9%EB%B2%95-%EC%B4%9D%EC%A0%95%EB%A6%AC/

However, when I copy another post URL, it is copied in lowercase:

https://vietnamguide.co.kr/???-??/
https://vietnamguide.co.kr/%eb%b2%a0%ed%8a%b8%eb%82%a8-%ec%97%ac%ed%96%89/

This issue doesn’t occur with all posts: most of them are recognised as lowercase, but some are capitalised.

I tried using the sanitize_title filter and canonical link as lowercase but not working.

   function lowercase_permalink_sanitize_title($title) {
       return strtolower($title);
   }
   add_filter('sanitize_title', 'lowercase_permalink_sanitize_title');

Is there any way to fix this issue and make all URLs appear in lowercase consistently?

Any help or suggestions would be greatly appreciated!