Do these have some sort of auto-cutoff feature? Occasionally, they will just stop firing in mid draw. The LED on my box mod will just shut off despite the button remaining pressed. I know it has something to do with the atty because I can remove it and keep my battery's LED lit for as long as I want. BOTH of my cisco 306s have this issue. That being said, they're great otherwise. This is just a minor inconvenience, really. Any help is much appreciated. Thanks!