Propane tank makes "pinging" noise.

We also had the same happen in our last RV and after researching found it was the valve or nature of that type. Keeping the tanks full helped. Also, in our current rig, when it gets really cold, our tanks will make a noise that sounds like a siren. Scared the heck out of us one morning up in the middle of nowhere to hear sirens early in the morning. It was the gas going through the lines. We don't always hear it but seems to occur more at high altitude.