Take a paper clip tip or toothpick and gently try prying up the 510 pin on the iStick, gently clear out any metal you see in there causing a grounding out from the pin to the threads if any, use a q-tip and a little rubbing alcohol to clean the connections. If that doesn't fix things then it is underneath the top cap, something is shorting out. Also check the pins and such of your tanks see if any wires are grounding the pin and thread wall.