Quote Originally Posted by cueball
...if you only have one clutch going at a time it's ok to put the thermo probe in the egg box. However if you introduce another clutch of eggs place the probe outside the egg box in the incubator. The reason being is that eggs generate their own heat(especially in the last couple of weeks). I hope this helps.
I had wondered about that...makes sense. If the eggs are generating their own heat, the thermostat gets confused and doesn't run the heat source as much as it should.