SNZB-02D versus SNZB-02P

I purchased a SNZB-02D. Unfortunately, it reports a temperature of about 4 degrees Celsius higher than that detected by 5 SNZB-02P (all tested in the same environment).

It must have some defect because it works with very good accuracy for me, there is 1 or 2 tenths of difference between the boiler thermostat vs SNBZ-02D