I have similar issue with ABC reagents as well, consistently getting Test A failure, not knowing its reagents related I paid Neptune $145 for a complete maintenance where they changed out the manifold, the tubing and mixing chamber, Upon calibration using the Fauna Marine's calibration fluid show Test A failure again when the unit shipped back to me, it was using the left over ABC reagents which I have 6 months supply of at the time I still didn't think it was the reagents reelated so I blamed Neptune by calling them again for their failure for servicing my Trident, they asked me to reset everything again and use the included authentic 2 month reagents included in their maintenance program, So that was a month ago when everything ran smoothly until the time to replace Reagent A, this time I went back to ABC reagents that I have laying around, Test A failed again. I immediately went to back to Neptune and everything is fine again. Maybe its a bad lot of reagent which I will approach ABC and see if they can kindly exchange it for me.