Messages group chat crashed on mac

Current status

So basically I have a group chat with some friends from school and its "crashed". Its a bit specific though because only that group chat has crashed (all my other communications are fine) and its only on my mac. My mac and my iPhone have the same apple ID. I can contact the group chat on my phone fine. By crashing (I'm not sure if this is the correct term) I mean that when I click on the croup chat on my mac the coloured wheel that spins around when something is not loading appears. After that my whole messages window freezes and I have to force quit.

How it happened

Okay so this is the important bit. It crashed on my laptop because I tried to past a massive amount of characters (I think like 9999 or maybe more can't remember). My group chat was just messing around with spamming and I got carried away. I know it seems and it is. It happened like a month ago and it's almost like the computer is still trying to paste the text.

Conclusion

So if you know how to hep me that would be great. Thanks so much!

[Edited by Moderator]