I put a sleeve on my copper Tesla, and that resolved the battery issue. No leaking down into the mod, and I have leaked quite a number of RTAs on it... It seems to flow down into the sleeve, not the mod.
The silver gunmetal I have as a backup doesn't seem to have quite the same issue with the battery door. I bought it a bit later on. Not sure if Tesla fixed the problem, but I'm saving it as a backup and using my copper with the sleeve as my main mod. Both 510 pins were fine, I also get great battery life, and I have no regrets about it. I also think it does TC well, it's probably my favorite mod for TC.... I don't know how the chip converts power so efficiently, but it certainly does. As a MTL person, I can't go below 7 watts, but that seems to work out quite nicely (the ST will not fire below 7 watts).
I have found the copper mod to consistently read about 0.14 high on all my atomizers, but since it's consistent, I don't worry too much about it, just adjust wattage...
I think (especially if you get a good battery door) it's kind of a steal at the prices you see now. I'm almost tempted to get another instead of a DNA mod, but I'm holding off on ALL vape stuff for now....
Anna