Propane fireplace valve keeps failing

[wrique]

I have a fairly new house (3.5 years old) that was built with a new Heatilator NDV42L-IFT propane fireplace. This is the 2nd time the control valve has failed. They are lasting about 1.5 years. When I remove the valve, I see water within the valve and rust stains on the output side ( first two pictures). The IPI pilot light is always turning on but the burners don't ignite (see video). I don't see that on the input side of the valve.
We seldom use the fireplace, probably less than 5 times during the winter for a few hours in the evening. I do turn it on once a month to make sure everything is OK.

Does anyone know why the valve (PN 2166-303) keeps failing?
Could it have something to do with the water? If so, what could be the most common cause of the water getting in? I don't see any water stain or rust on the vent.
Could it be the controller? I hear the 2nd beep when it is supposed to turn on the main burners. I also reset the controller and that didn't help.

 

[blades]

I do not think you should have water inside the valve. Suggests that the propane tank is contaminated. Water forming on outside of lines is possible in a high humidity environment.

 

[wrique]

I'm not so sure about the propane tank. I only see water on the output side of the valve and I use the propane tank for my pool heater, water heater and BBQ grill with no issues. I'm wondering if I am getting rain down through the fireplace roof vent coming down into the burners and into the output side of the valve. Could that be possible? Taking apart the fireplace burners looks difficult.