At the end of most rounds I’ve found that sometimes after rounds in the win screen/in the lobby it no longer allows you to chat. You can type in the message normally, but when you send it nothing happens. If you spam messages you also don’t get the “Spam Filter” notifications like the server isn’t even getting sent the messages at all. Typing “Say Hi” in console also results in no chat being displayed in chat box.
One thing to note, I’ve noticed when chat is being blocked in the win screen, if you enter the roll/coin toss command it displays the system message in chat box still, so I don’t know why the normal chat wouldn’t work.