Absolutely inaccurate

Netatmo is basically time a great and innovative product. Facility, feel, operation, etc. are really good. But the accuracy of the measurements are underground and do not match the product specifications agreed.
I bought the base station and the external module together with another indoor unit. All 3 I have 10 days placed on my desk next to each other. Despite all attempts to calibrate fluctuated all measured values ​​of all 3 stations (temperature + - 2 °, humidity + -8, CO2 um50%). For reference, I used an additional electronic and analog hydro- and thermometer. These always showed coincident values.
Unfortunately, I can only advise against Netatmo ;-(