Spamming certain characters crashes the game.

People can spam messages that look like graphics (buttons, controls, etc.) in chat. Repeated use of this can cause the game to crash. Mostly happens on LAN servers or realms, even if you're the owner or just a player. I don't suspect this can happen in servers because of the delay in chat. If they stop before you crash, you can play the game at about 20-30fps, but you will get insane lag spikes that leave your game to freeze for about ten seconds. The only way to stop the lag spikes is to get rid of the text, by re-entering the game, or spamming the chat with numbers and letters until the graphics go away. 

I added onto some of this description in the comments.

 

video for newest version: https://youtu.be/cMUvJhPt5iw