Something really weird going on with mine... initially I thought it was the black o-rings, replaced the bottom one with the blue and it started working perfectly. Last night I tried putting the other blue one (top) back on and no matter what I did it leaked! I re-wicked 3-4 times, went back to the black o-rings, made sure the one in the chamber was still there, no luck! I then put it on another mod and no more leaks, using the black o-rings. Is it possible a mod could be pushing the 510 pin too far and causing it to open somewhere and breaking the vacuum?
The mod with the leaking is a Presa 75, it has not leaked using the SX Mini. If you look a few posts up you'll see that it's also working with the SX Mini using the blue/black o-rings. I can't recall if I was using the Presa when I had the problem earlier and thought it was the o-rings, but it's possible. I usually grab whatever mod I have handy.
The only other thing I can think of is that I use an ultrasonic cleaner to clean the tank. I used it both times just before I had the leaking problem, I was changing flavors... it has a built-in heater and I use it, and run it for about 20 mins. It's possible that it just needs a while to cool down, but I doubt it, it was plenty cool when I was re-wicking it, even rinse it a couple times with cold water once it leaked.
I'm all out of ideas!

My GF is using the other one on a eVic VTC Mini, I re-wick it for her every few days, she has had no leaking issues.