I am wondering if there’s been an issue with their calibration solution due to pandemic sourcing issues? It seemed to start after that for me when the reagents became hard to find.
I have a feeling that it has more to due with the Ca and Mg reagents. They will calibrate to what you tell them, and seem accurate for a while. Then the readings start to drift as the reagents get older. Alk doesn't seem to suffer from the same problem.
In my experience, the longer it has been since the reagent has been changed, the less time it will hold calibration. Also the further the results will be off.
Right now my Trident is reporting Ca over 100ppm low... Frustrating.