ok just to make sure I am reading this right, your using a Low Resistance atty at 6volts?? Unless i am seriously wrong the over draw safety mechanism is kicking in preventing you from blowing up your batteries. Low Resistance attys are designed for 3.7 volts and simulate higher
vaping by pulling power quicker from the battery, if your trying to pull power quickly from stacked batteries (that are unprotected) the gas expands and they blow up, however yours are protected and its that protection circut thats reading the over draw and turning off the power, and lucky for you. Why would you need LR on top of 6 volts? at 6 volts all attys will blow tons of vaper out, should be no need for LR. Try using a regular atty or even a HV (High Voltage) atty at about 2.8 - 3.4 ohms (thats ohms NOT volts, LR attys are 1.5-2.0 ohms) and this problem will go away, if it does it was your batteries safety protection kicking in.
I could be wrong about this so if I am someone please post to state i am. Is this your first time trying a LR at 6volts? I have just never heard of it, and i owned a silver bullet, usually people that use LR on silver bullet are using a single battery at 3.7 volts.