One second, the app was fine. Then it just vanished. There was nothing wrong with that app: it was murdered. Join this game of Cluedo/Clue in macOS.
unexpected quit
The current macOS implementation of preferences is appalling design in every respect, and is essentially undocumented even for developers. Is this the way that macOS is heading?
Have you ever tried removing or editing a preference file, to no effect? This explains why that happens, and how to get changes to work properly.
Problems with preference files can easily crash an app, even when the file looks fine, and its permissions are correct. Here’s why and how.
Tread carefully in the Print dialog of Contacts: its liable to cause an unexpected quit.
The computing sense of crash lacks onomatopœa, is gross hyperbole, and is far too widely encompassing to be meaningful.
The Eclectic Light Company 