Jenn-Air Oven Temp Issues

Recently, we started seeing oven temperature issues. When we set the oven to say, 300 – it would normally take about 3-5 minutes to heat up, after which it would beep indicating that it had reached that temperature. Now, when we set it, it beeps after just 30 seconds and the oven is barely warm. I thought it might be the oven sensor, so I replaced it, but the same thing occurs. Is there something else I should be looking at replacing? Some of the electronics, say?

Thanks very much,
JPG