I have a 1 1/2 year old MB 20050716 Masterbuilt Propane smoker with the glass door. It worked fine for about 4 smokes, but now, it will not stay lit. When I go to start it, i push in the selector and turn it counterclockwise to high like it saves. When I hit the igniter it roars to life, and as long as keep the selector pushed in, it stays lit. I have kept the selector pushed in for as much as 5 minutes, but every time I release the selector, the gas shuts off. I have done this for almost an hour and it shuts down every time. I had to use my Smoky Joe stick burner in 90 deg weather for my ribs. I believe the gas shutoff system is turning the gas flow off but I do not know how to either remove it or fix it. Does anyone have any ideas. I love the Masterbuilt propane smoker but it is unusable if the fire will not stay lit! HELP!