My oven is not maintaining a stable temperature

Oven/Range/Cooktop Repair
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1

Brand: Samsung
Model Number: FE710DRS
Main Symptom: temperature is not stable
What happens & when: Cooking is unpredictable. Sometimes it takes forever to cook things. Bread will not rise/cook properly in this oven, never browns on the top, doughy center but dried out.

Error Code (if any): none
Parts or tests already tried: Tested the temperature sensor, correct Ohms. Recalibrated temperature but it ranges up to 10 degrees off compared to 3 different oven thermometers. Temp is unstable using Bake and Convection Bake. Both convection fans are working. Oven is 14 years old.
Photos / video link:

2

Based on the information provided and the probe checking out good, the control would be the next likely cuprite.
https://www.appliancepartspros.com/samsung-assy-pcb-sub-de92-02440d-ap5653303.html