Getting the error "You have been disconnected (WOW51900209)" on specific characters

The characters in question have originally been created on a server with Russian language, and all have names typed in cyrillic.
I’m trying to log in to the Bloodfeather realm and getting the error “You have been disconnected (WOW51900209)”.

What is causing the error? Is it because my characters were created on another realm? Or because the names of the characters are cyrillic?
What can I do to solve this issue?

I already visited pages like Common Technical Issues and Solutions and Connection Troubleshooting.

The actual connection doesn’t seem to be the issue. I can connect to servers with Russian language with the characters in question. And I created a new character (since deleted) with the name spelled in latin characters specifically to check if I can connect to servers with English language which worked fine.

So my question is, what can I do to connect to servers with English language with my existing characters?

Just to reiterate, the issue is, I can’t connect to English servers with my existing characters named using cyrillic characters.

I suspect that I need to change the names of the characters, but it’s a paid service, and don’t want to spend money on something that might not work.