I'm on my second blue carbonator cap. The first one cracked, after having never once succeeded in sealing on bottle threads. As in CO2 hissing out loudly while I was trying to pressurize a bottle. We're not talking a tiny leak. We're talking practically zero seal. The second one, bought mere minutes ago, is doing the same thing on every bottle I have tried. I have cranked down as hard as I dare on the thing--that's how I cracked the first one--to get it tight on the bottle, and no dice. Hence the question in the header. Do these things ever, ever, EVER work??? Or are they just expensive garbage?