It is possible for a user to fumble the target calibration process, and successfully save invalid calibration parameters. They'll then encounter an "Invalid calibration" error when trying to take a measurement.
This can be most easily reproduced by doing a reflection calibration, then measuring the CAL-HI patch before the CAL-LO patch. The calibration routine does not check the relationship of these readings, but the measurement/settings-get routing does.
It is possible for a user to fumble the target calibration process, and successfully save invalid calibration parameters. They'll then encounter an "Invalid calibration" error when trying to take a measurement.
This can be most easily reproduced by doing a reflection calibration, then measuring the CAL-HI patch before the CAL-LO patch. The calibration routine does not check the relationship of these readings, but the measurement/settings-get routing does.