With any Electric there is going to be a difference between Set Point, Unit Measured Temp and Actual Temp (MAV) because of overshoot of the setpoint as the coil shuts off, cools and all equalizes. You must have the Mav probe reading very close the the sensor that reads measured temp to be accurate. Up on the racks the MAV will read something different. If you also didn't move the Meat Probe to the same location of the others, It will measure the temp in it's location and be off of the others. I suspect this may be the reason for your result. Get all the probes in the same location and see where you are at....JJ