I bought the STU about 2 weeks ago and have a few questions about the rear screw cap. The first time I tried screwing the cap off, I thought I broke it, since it made a loud popping sound and came loose again. I figured it was ok, because it still screws on relatively tight; however, if I screw it as tight as possible, it comes loose again. In other words, it's never perfectly tight. Is this normal, or is mine defective? Also, when I'm FLying, the suction cap makes an annoying whistling sound as if air is escaping, and then lube inevitably escapes as well, oozing out from the seam between the case and suction cap. I'm almost tempted to tape the end cap, so nothing can escape. Do others here have the same experience?