Just a little addition from me: I have had some issues with the thermometer with both my Brinseas (Octagon Advance 20 with external humidity pump, and Advanced Eco for 7 eggs). One shows too high temperatures, and one shows too low temperatures. The temperature is constant, so once I figured out the difference, I just changed the temp settings and everything was fine.
I know more people who have had this problem, so I strongly advice to buy a precise thermometer to check the temp before starting the incubator, and occasionally throughout the hatching. Supposedly you can fix the calibration yourself, or send it for recalibration with the supplier. So far I haven't bothered - it works just fine as long as I correct for the temp deviation.