Penman, I had the same problem on our new Wildwood Lodge. It was coming from the cylinder on the street side of trailer. I switched the cylinders from one side to the other. I still had the pinging sound. The dealer replaced the regulator which helped for a short time. The pinging returned and it was ALWAYS from the street side tank. One time when it was pinging I happened to grab hold of the pigtail that goes from that tank to the regulator. I could feel a vibration in that pigtail. Dealer replaced that pigtail and no more pinging.