Some characters such as russian letters are converted which makes it impossible to perform a search query from website

[Ismayil Mirzayev]

I use Azerbaijani and Russian letters on my website. Sometimes some letters are converted to something like this {"az":"Velosiped","ru":"\u0412\u0435\u043b\u043e\u0441\u0438\u043f\u0435\u0434"} but sometimes it doesn't do this. I thought maybe it's some specific letters but it's not the case. I need to manually change it back to how it should be, but I've thousands of data. They display correctly on the website, but a user can't do a search because it won't match.