Some thoughts (and yes, I'm getting very frustrated too) Different juices? Bad connection somehow? Coils bought on e-bay? Not well primed? Airflow set different? Wattage used different? "Negative " pressure within tank as juice gets lower?
Most of my issues were from not priming well or from not letting coil cool a bit between vapes. Then I broke down and got some off e-bay... half were defective! Now all of sudden, using the same authentic coils I've been using, got 2 from the same 5-pack acting up for no reason. They seem to have restricted airflow (cotton and/or coil installed wrong?) Maybe just a bad lot? Opening a new pack soon and better not happen again!!! By the way, that thing about neg air pressure... when the tank gets about halfway, open it up to let air pressure in... seems to help. Also, I'm OC now about doing "primer puffs" between vapes... helps keep the cotton saturated. I am so wanting a RTA (I actually have a dual coil RDA/RDTA but need a better mod to run it) Tell us the tank and coil details anyway... might help (mod shouldn't matter unless it's an issue with conduction to 510 on tank) Yes, I tend to get a week (or more with TLC and the right juices) but have had coil act up in less than 24 hours and that sucks!