When I upgraded to 11.4, I noticed that knotify crashes quite frequently. I found an old thread about this, and it seemed to be a problem with whenever knotify made sound, and that seems to be the problem. This happens whenever I log on, log off, or receive an e-mail, and when I changed the program with which the sound was played and received an e-mail, no crash occurred. I am going to log out and back in now to see if the workaround removes the crash during those scenarios.