We have a Hotpoint LP gas oven that comes on, heats up but won't stay at temp. It heats to 325 when set on 350 (which I could live with) but goes down to around 220, the burner ignites again but only stays on until it reaches 250 then goes out again. Never does get back up to 350. I have to turn it off and back on, it goes into preheat mode and the whole thing starts again. Tested the sensor (tested 1086 OHMs) and the igniter checked out, glowing orange for 1 min 42 seconds before it lit and stayed on during preheat. Any idea of which part needs replaced? None of the FAQ's addressed this exact problem.