1. Reproduce the problem or wait for the problem to happen again. If an error message appears, leave the error dialog on screen.
2. Capture a screenshot. (The timestamp will show us where in the logs in to look.)
3. As soon as you see the problem happening, hit Shift-Cmd-Ctrl-Opt-period to trigger the sysdiagnose. The screen should flash to indicate it has started.
4. When it is done, Finder will open a window to the location of the log file in /var/tmp/. Attach that file back to us, as well as the screenshot that you took.
5. If Feedback Assistant is not in your Dock, you can launch it from Spotlight or use feedbackassistant.apple.com to upload the file.