ToString can only be called from the main thread.

I know there is aleardy a question with this topic, but I do not use .ToString at all or any other method that converts something in a string. Even if I search with strg + f. I am using Asynchronus Sockets to communicate between my server and the game.

ToString is a framework method that every object and value has. It might be called implicitly whenever you try to concat a string with and object / value. Don’t you get a stacktrace with that error?

You didn’t show any of your code and you didn’t add anything specific that would help to identify your issue. So there’s no way we can actually answer your question. The only thing we can say for sure is that you or any other method you call does indeed use ToString of an object that is not threadsafe.