I read about this reproducible crash for OSX, mojave, As soon as you use the Free Transform tool and move the selection it crashes each time.
I have enough problem with the software and brush sensitivity not working for me with a 2018 wacom tablet, now this.
I already uninstalled the application, I went ahead and downloaded the latest version the app store offers, and reinstalled. The program is still buggy and needs to be fixed.
Paintstorm is a good program just very buggy unfortunately.