BME280 long term drift of readings

I am running many BME280s in a moderate humidity environment (between 50% and 80%, at around 20C) and am seeing around 10% of the  units reporting more than 5% off of what our reference sensor reports in the same environment. We use a hand held sensor like this as our reference. Since these devices have been deployed for less than a year, there is concern that this drift is outside of what is characterized in the data sheet. Is there a more detailed aging reference available?