Greetings. Have a twenty year old natural gas Stove/Oven unit. Still works well until a few months ago. The oven temperature is off and items are being over or under cooked. I placed a thermocouple in the middle of the oven, set the oven to bake at 275F. Oven temperature rose to 308F, burner turned off, temp slowly dropped to 266F before burner turned back on and repeated this cycle.

My first question - should the oven temperature swing this much ?
My second question - is the Temp Probe connector easily accessible behind the rear cover of the range ?

It appears to me the control board seems to be working properly as it is turning on and off the gas burner. So my third question - is this issue more likely the temperature probe failing to provide proper voltage signal to the control board rather than the control board managing the gas valve feeding the burners in the oven ?

Appreciate all feedback - Thanks in advance,