Hi, I just recently got a Mig. Cheap and bad, but that's not the point here. I use a 5 kg bottle from Albee Air Liquide (https://industri.airliquide.no/gasslevering/gassflasker) with a built-in regulator and a snapon fitting that came with it. When I open the valve, gass is leaking out. actually that much that I not only can hear it, but feel. I attach two pics from the connection. As the fitting came with the bottle, I suppose it is the right one. Does anybody know if these things have a gasket that might be missing?