I've noticed this before but as I just wanted to copy the japanese name of Drifting Dragons (https://www.mangaupdates.com/series.html?id=135805) into the search engine on a japanese website, I was greeted with no search results. Afterwards I tried looking for the japanese name on another website and tried copying it into said search engine again. This time I got results.
However there's no apparent difference between the two names so I think there's just something wrong with it's coding.
Copying the JP name both from here and from another website into Notepad++ will also result in some weird looking characters for the text copied from MU.
Upon further searching it seems to be a problem with the katakana symbols.

This seems to be a new bug introduced some weeks or months ago.

Do you have more information? Like the exact search engine you were using that yield no search results. And where you copied from that ended up getting results in the same search engine

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A just ruler amongst tyrants

Try bookwalker.jp
Also just try pasting the text into notepad or any other text program on your pc and you should see there's something wrong with the katakana symbols. https://i.imgur.com/p177BlC.jpg

This should be fixed. We were encoding using NFD instead of NFC. I switched us over, and did a quick conversion of the database. Let me know if you have any issues.

Seems to be fine now, thank you.