Hello: it is a failure of the gas command. It is a repair that corresponds to the technical service claims to the guarantee, do not mix the water overheats and increases the pressure much you can break the appliance or the hot water pipe as a test until When the technical service arrives, you can try to lower the gas flow from the stopcock with the heater on. Start to close the gas valve gradually, observing that the flame shrinks without the device being turned off so that you can use it.