Well it's best to actually use a fake egg and make sure it's actually averaging out in the middle as expected because it could shift up or down depending on the duration of the cold and hot cylces..
One thing people seem to miss or that skips their mind while they are so focused on 99.5° 'air'...
There very well might be nothing to fix, your thermometer is measuring the 'air' temp and that can easily swing with the cycling of heating elements, depending on the swing of the thermostat circuit... The mean average of 102° and 97° is a dead on 99.5° and that very well might be your internal...