Before the next batch of eggs, I would try and see if you can run the bator steady and check temperatures every 2 hours or so through the day at egg level. Try this at different locations in the bator and get a better idea of where there are hot or cool spots in the unit, and if the unit is keeping temps continuously during the day or night if you can check on it. If there is a wafer in the bator, might try replacing it.