I've experienced both instances of the "tap/swipe = double tap" and the "erratic behavior with touch screen and navigation buttons". I've replaced my phone under warranty twice and occasionally have these problems with my newest device. I've noticed the erratic behavior is most definitely a hardware issue. Because the device is so large yet so thin, the screen flexes under less pressure than smaller or thicker devices. This causes numerous tap events to register in different parts of the screen, causing the erratic behavior. The single tap and swipe issue is most likely a combination of hardware and software issues. It's entirely possible that a hardware defect in the LCD panels used in the 1520 is making it difficult to tune the drivers for the touchscreen digitizer.