Socket.io Connection drops when sending Russian letters on Ubuntu?

Question

Node.js

OS Ubuntu
The same code works on another server on CentOS, the client also works without errors.
The problem is only on this server.
Everything works fine until {mes:'something in Russian'} is sent
to Node, no errors come out, the client is reconnecting to sockets.
Gives away sometimes

WebSocket is closed before the connection is established

For the whole day of searching, I could not find anything.