Erraticoven temperature

The oven temperature is erratic. When set to 350 it will randomly spike to over 500, no faults and all other controls seem to be fine. Some times it will work fine but most of the time not, especially if it has been operating for over an hour. I have replaced the oven sensor but the problem still exist. What receives and interprets the signal from the sensor? Is it the control board, is replacing that the next step. Thanks in advance for any advise. – Jim