I have a Whitfield Optima 3 insert that is six years old. This is the first year I have problems with it. And do I have problems. The stove will start and run for about 20-30 minutes and then go out. During the burn session the fire will burn nice like it should then die right down to almost nothing then feed more pellets and then be OK for a short period. So I figured the flame sensor was the culprit. So I replaced the sensor and cleaned the lens. No luck, same problem. So after checking the forum, I read of problems similar to mine and they suggested changing the 2 thermal switches, so I did, no difference. I made sure the stove is good and clean, the flue is clean, checked the pressure switch and that is OK. Now I don't know what to try other than replace the control, which everyone knows is a bit pricey, so I figure I would see if anyone had any suggestions that maybe I missed before I take the big plunge. Any suggestions at this point will be greatly appreciated. Thanks, Charlie