You're one of the weird ones IMO. Which, don't get me wrong, I WISH I was one of the weird ones who can discern a deterministic trend when testing PO4.
Everytime I've complained about the numbers I get, I get 1 of 3 potential replies (I even took my concerns to Hanna directly when I was using the predecessor of the checker, a larger blue coloured photometer that retailed at the time closer to $300
)
1) Your PO4 is low enough, stop whining (never mind the PO4 related symptoms in the tank they must be because you are crazy)
2) Those variable readings are well within the specified error range, so you must be crazy
3) Mine works just fine so you must be crazy. I just took a single test reading on my tank, it said 0.00, and I only need one test per year to know that this is correct.
4) (I never said I could count) Did you try cleaning your test vial? It has to be very clean. Oh you clean the test vial beforehand? Then you must be crazy. Oh wait, did you try cleaning it with
RO/DI? Oh you did. Well fine then, you must be crazy.
If someone would just hand me the @#$%!!! koolaid, I would happily drink it.