All relevant product information can be found on the Analox Sensor Technology website, take a look at the O2NE+and Safe-Ox+ product pages.
The oxygen sensors used within the O2NE+ and Safe-Ox+ are both sensitive to mechanical shock. Readings that remain stable unless the device is tapped / bumped usually indicate that the unit has experienced a large mechanical shock (possibly dropped prior to installation).
The O2NE+/Safe-Ox+ device should be returned to Analox for investigation and repair.