My propane water heater has been acting up. It seems to have two problems (maybe related). The flame sensor does not seeme to be seeing enough flame? since the burner turns on proberly but quickly turns off after a couple of seconds. I have tried to clean the flame sensor and sometimes this works which leads into the 2nd problem. After the burner finally stays the flame poofs out every few seconds but somehow stays going. I am not sure why the flame does not stay on full until the thermostat tells the system to turn off. Could there be some blockage in the orifice of the burner?