Twice in the last week after using the lower oven, it beeps and displays F22 after being shut off. I had to shut off the breaker for a while to get it to stop from coming back on. We've used it multiple times over the last week and it did not display the error every time.

My wife didn't think it was heating properly a couple times, so tonight I put a temp probe in it. I preheated to 425 with convection bake. Even though the oven said preheated, the temp probe reached 360 at the highest before actually starting to cool down and get as low as 310! At that point I shut it off and heated the top oven to 425 to cook dinner. My probe reached 400 and was rising when the oven reached preheat of 425, so I pulled the probe and put in my dinner. Sometime after I had shut off the upper oven, the error appeared on the lower oven display.

My searches on the internet point to replacing the control board (mostly) or maybe cooling fans. Is there anything I can test to get a sure answer?