I share your frustration with unreliable kit and inconsistent procedures, but how does having a second chrono help? Is it logical to say, I will use chrono number 1 until I get a result I don't think is right, or I don't like, and then I'll reach for number 2. Isn't it better to scrap number 1 and just use number 2?
Having three chronos just adds further confusion. Which one do you trust? Is it reasonable to assume that two giving a similar result are correct, whereas a third with a different result is erroneous? Maybe the third one is actually number 2, that we turned to for certainty in the above paragraph.
Field testing is never going to deliver the accuracy and consistency of a lab test. Maybe we have to place less slavish reliance on site testing, or at least recognise that there should be a tolerance applied to the output, and appropriate decisions taken accordingly.