Way back 35 years ago I held a state grain graders license. Was told at grain grading school to not re-test the same sample. Said to use Boerner divider as many times as necessary to reduce the sample to the amount needed to test. If you want to re-test sample, run untested grain back through divider as many times as necessary to reduce sample and test that sample. He showed us the result of re-testing the same sample over and over. I don't remember if sample moisture increased or decreased. He showed us the same results using several brands of bench type testers. Had a large Dickey John tester, a farm duty Dole and Radson, a Steinlite, and a couple others. Showed us how inaccurate the hand-held testers of the day could be. Hand-held testers needed to have a good representative sample and multiple samples tested and averaged. Grain testers of the day measured moisture by capacitance. I'm sure technology has changed a lot since then, but then again, maybe same principles apply. I haven't seen a big old copper Boerner divider used in years.