I have a Whirlpool gas stove model SF315PEPW1 that is having an issue with the oven. We set the temp and the oven lights (sometimes takes 2 minutes or so to light…I’m assuming this is normal). Once the oven reaches temperature it turns off, but does not come back on unless I light a top burner otherwisew it just cools back to room temp. Now we bake with a top burner on low and the oven works correctly. What part needs to be replaced?