Erik, the top of the head seats against a rubber gasket, like an o-ring (maybe black silicon) where it screws into the center chimney. I have had the same experience as you if I'm holding the glass tank instead of the top metal while screwing the tank together. Sometimes if the top isn't screwed on tight enough the glass can start unscrewing just a little and a good seal isn't made against that gasket. Better just to hold the metal at the top while screwing the base with the head on. If the head doesn't seal completely it can draw in air there instead of through the head causing the same symptoms you describe. The glass unscrewing just a little will make the length too long for that seal to be made, but juice won't leak outside the tank since the top and bottom seals of the tank are still being made. Makes it hard to see what's going on. I found this by accident and I'm not sure if this is what happened for you, but thought I'd mention it. Fortunately, it's easy to fix and not really a problem once you realize what's going on.
