I have a Warm Morning propane vented 10,000 btu heater in an old house. This winter we have been having a problem with the pilot light going out once or twice a week. The pilot light relights just fine. Sometimes, when the flame is on in the heating cycle, there is a loud, constant puffing type noise. I thought it was the fan, but when the flame goes off, the noise stops and the fan is running fine. Sometimes when the flame comes on, there is a loud puff. We had someone come out and look at it, but they couldn't find anything wrong. Can you give me a clue as to what might be going on?