First vari-valve failure

Daniel_3

After the 30 or so Heat Timer vari-valves that I bought and installed between some properties, mostly my own, I had the first failure. I like these vents but hope that this is isolated to this one vent. I had tapped and installed a second on an upstairs rad and found after several months that it suddenly stopped charging with steam past the first section. I blew into both valves to see whether they accept atmosphere and lo the bottom one didn't. I took it off and found that you can blow the bellows closed with little pressure. When you blow out through the vent it kind of mutters with an uncontrolled flow rate. I assume this vent is failed to some extent but without opening it up I don't know for sure.