Hi.

If any oven is reaching 400 degrees even if it may take longer, the bake element has to be normal! Which leaves out the control board. I would replace it, besides you can always return it back installed or not within one year. But because the broil element is also involved in the heating, before ordering the control board you should run the bake element continuity test at its contacts with one wire off. Don't forget to unplug the unit.

Thank you,

Simon.