The crackling sound is perfectly normal. The screen scrolling probably is also, but I don't have an iStick 50 so I don't want to swear to it. On most of my regulated mods, the numbers move when the button is pushed. The deal is, when the button is off, the display shows the settings. When it is pushed it shows what's actually happening in real time. And yeah, that can move around some. It's probably actually volts that are moving around, not amps. As the coil wire heats, it changes it's resistance-- all metals do this to some extent-- and thus the volts have to move to keep the set watts in the same place. See Ohm's Law for a complete statement...