Magnesium checker inconsistent/inaccurate?

[DeltecUSA]

I have been using a Red Sea Magnesium Pro test kit. The kit was opened 9/17/22. I had been consistently getting numbers between 1450 and 1500 even after stopping Mg dosing (I use ESV salt which has an option to add Mg to the mix thinking I had added way too much somehow). After reading that the Hanna Mg Checker's issues had been resolved, I decided to purchase one from BRS two weeks ago. My Mg numbers have been surprisingly different from the Red Sea numbers. My initial reading was 1200 on 11/27 and even though I have increased my dosing by nearly 50% I'm still at a high of 1230. However, I did 3 tests today and came up with readings of 1135, 1100, and 1230. This was after a 30% increase in dosing from Sunday which had a reading of 1180. That is a significant fluctuation in numbers. The Red Sea test is still at 1480. I have the unit with the built-in 3 minute timer so I'm pretty sure I have the correct version. Are there still issues with this Checker because these numbers are all over the map and I'm not sure if I can trust this Hanna unit?

 

[SeeFu]

mine is very inconsistent too. i use trident and red sea test kit and those 2 are always withing 20ppm of each other. first time i used hanna, it read 50ppm higher. today it read 100ppm higher.