My Whirlpool Model# WOC54EC0AS02 electric oven is doing thermal gymnastics. I Bought a digital thermometer to record the problems, and since have tried to repair to by replacing the thermostat and the sensor – nothing has changed. I set the oven at 350 the thermometer reads 395, I set the oven at 300 the temp inside is actually 395, I set at 400 it comes in at 540. I recalibrated the oven (it allows for +/- 30 degrees) the maximum in both directions and then turned on the oven to 350. Both times (increase and decrease) the oven heated to 395 and held. Takes forever to preheat, then seems to shoot to high temps. What is going on? This has me baffled.