 FootNotes not working with Russian

Hello!
Thanks for this app. It works well, but I don't think it works with Russian. This doesn't work in TinyMCE and after posting to html. I am attaching an error example. 
<img width="650" alt="image" src="https://user-images.githubusercontent.com/68350213/174481901-c503d155-cd93-48bd-970c-4090135ec8a2.png">
