App freezes on one of my threads

When I click on one of my threads in the app, the entire app freezes and the fans of my PC start ramping up. It happens only on one of the threads each time. I don’t remember what the thread was about but I don’t think it was a long series of messages. I only recently logged in for the first time and was using the app before that. The messages probably did not hit the 10 message limit in that thread.