Hello, I decided to try out the Ultrafire BRC18650 3000mAh batteries, dude to the short performance of my AW18650 1600mAh batteries (3hrs). One thing I noticed was that the Ultrafire is almost 1/4" longer, it still fits, but its tight. I've been using this for about 3hrs with a Boge LR 2.0ohm carto @ 4.2v and now something strange is happening. If I draw on the unit for more than 5sec, it just shuts off...no error code, no flashing lights...nothing. I then have to unscrew the bottom cap and screw it back on again...hit it a couple of times...then, It happens again. Any input will be appreciated.