First here are some pictures I took a few years ago when I had problems cooling on LP. I thought at the time I had a good flame at the burner.
Cleaning the burner tube and the jet made the difference. You can't see the jet in these pictures but if you look to the left of where the burner tube is in these pictures you will find it. You need to remove the burner and you can get to the jet and unscrew it from the gas solenoid.. You can soak it in alcohol a blow it out with air but NEVER try to poke it with a piece of wire.
A couple of years later I had low flame problems but it turned out to be the LP regulator.