Frigidaire Gas Oven Wont Come to Temp

Hi:

My gas oven (frigidaire FGF366DCD) is 6 years old. The gas oven works, but we have to use an internal thermometer to get to the right temp. For example, if we want to bake at 375 we have set the oven 75 f (or more) higher. So in this case we would set the oven at 450 to heat it to 375.

I am assuming, but wanted to check, that the temp probe needs to be replaced.

Thoughts would be appreciated

Thanks