Oven not getting to temp

Hey, I have an oven here that is about 50 degrees off. Control board reads 350 but the actual temp hovers at about 300.
Spark ignitor works. Oven turns on as it should just doesn't get up to temp after the initial preheat. Temperature probe ohmed out at 1100 at room temp. At 300 degrees it ohmed out at 1600.
The tech sheet available was the French version. Not fluent...
Wondering if this unit can be calibrated?

Thanks

via Oven not getting to temp
by Mcnabb75