I don't know what all you have or how it's ran but i do know that the GC valve has been known to stick from time to time, I have found that if i give them some sort of back pressure then they stop sticking. but that is more or less for the dump valve. like taking a 1/2" dump valve and use about 3"s of 1/2" copper line and then crimp the end down just a little at a time. but that is not the case for the fill valve. they get pressure from both sides of the valve. But if it was my problem then i would do what "bagtodrag (
Brian@KEGMedia)" was talking about. Good luck with the sticky problem bro..