GRIDDLE BURN BACK
Burn-backs happen when there is an obstruction in the manifold valve or pipe itself, that keeps the L.P. Gas from flowing into or through the the burner pipe properly. The obstruction will cause the L.P. Gas to flow back around the mouth of the burner and under the control panel. Once enough gas collects, it will ignite if the griddle is lit. The best thing to do when you first light each burner is to take a look at the flame. If it's yellow, or orange, or it's jumping, you have a problem. The gas and oxygen mix is not right. You will want to shut it off and check to see that the burner pipe has not moved. Make sure the valve is sitting squarely in front of the mouth of the burner tube. If that looks good, you will want to clean out the pipe and valve itself.
An obstruction can be caused by grease, debris, insects, spiders' nests/web, just to name a few. Regular cleaning of the burner pipes and valves will prevent burn backs.
These are some products recommended for cleaning the valves: Valve Cleaner