Had this happen on my Broadwater. The problem (for me) was in the gas knob I was pushing. The sensor in the flame actually causes a current to flow in the tube that come back to the valve. In the valve there is a electrical coil that create a magnetic field that holds in the plunger (to keep the gas flowing) This electrical field is very weak and can only hold the plunger in, if the plunger has been pushed all the way in, by the person pushing the gas knob.
In my case I was pushing the knob in on the stove but it wasn't quite moving the plunger far enough in so the magnetic field could hold it. The gas control knob was hitting the face plate on the stove and stopping. I put a piece of packing inside the hole (in the knob) where the knob fits on to the valve shaft (shaft is what sticks out of the stove when you take the knob off). This meant, when i pushed the knob in, it made the valve shaft (hence plunger) go in a bit further and the magnetic field was able to hold it.
Maybe this may help.