It's hard to say what is wrong without the wiring schematic for the oven. Unfortunately it is not available on line due to its age. If you do have the schematic and can post it, it might help to diagnose the problem. You can find it inside the control panel.
Here are the breakdown diagrams and
Replacement parts for WHIRLPOOL KEBS277WBL0 | AppliancePartsPros.com
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