Make sure your calibration cap/calibration tile is clean. A dirty calibration cap/tile can affect the result of the measurements, as your Colourpin will be calibrated incorrectly. In this case, clean the lid/tile.
If you have access to official NCS samples, then try to measure 20 of these samples and see what the results are. If more than 1-2 samples show wrong results after measurement, please return your Colourpin.,