BMP388 Accuracy

Hi.  I am looking at using the DFROBOT BMP388 module (SEN0371) for a weather station.  I am using the DRROBOT library for the BMP3XX, connected to an ESP32.  

The weather station will be fixed.  I have used the  calibratedAbsoluteDifference(elevation) function in setup() to set the altitude, since it is a fixed station.

Even after doing this the Pressure is reading quite different to that reported by our Weather service (BMP388 says 1008 hPa, actual pressure is 1019hPa).  Also, after a couple of hours the altitude has drifted from 37m (set using the function above) to 57m.  I am using the eUltraPrecision sampling mode.

Any suggestions about how this can be fixed, are there any other calibration functions available?  

Gerard