I had a 30 lb cylinder recently that had the same problem. Wasn’t the auto-switch regulator, wasn’t the pigtail causing the problem. I ended up having to have the tank valve replaced. The LP dealer tech confirmed the problem with his equipment. I don’t know what can go wrong with the OPD valve to make it fail that way, but it did.
Fortunately, the valves aren’t expensive, and it counts as a tank recertification as long as they mark the tank accordingly.
:):)
2001 Lance 1121 on a 2016 F450 ‘Scuse me while I whinge.
And for all you Scooby-Doo and Yosemite Sam types………..Let’s Go Brandon!!!