The female ACME nut on the hose end has a check valve built into it to prevent gas trapped in the hose from escaping. If yours leaks
when disconnected you need a new hose end. This applies to green, red and black ACME nuts.
Quoting from the Marshall Excelsior RV catalog, page 24 https://www.marshallexcelsior.com/si...%20Catalog.pdf
The Type I (QCC) connectors (ME517, ME518 and ME519 Series) are designed with a built-in excess flow feature and a positive shutoff that will not allow gas to flow until the connector is fully engaged. In case of a fire the built-in thermal protection on the QCC connector melts allowing the nipple to disengage from the tank connection and stop the flow of propane. These QCC connectors also provide a positive back check seal at disconnect to eliminate the propane in the hose from being released into the atmosphere.
To connect a Type I (QCC) connector to a cylinder, close the cylinder valve and the control valves to all connected appliances. Hand tighten the QCC onto the cylinder and slowly open the cylinder valve. If the valve is opened too quickly, the excess flow device will be activated closing the flow of propane to the appliance. If the excess flow device is activated, close appliance control valves and wait 60 seconds to allow pressure in the line to equalize. Additional equalization time may be needed depending on the length of the hose. Turn on appliances by following the manufacturer’s suggested lighting procedures.