Yeah, I don't know nearly enough to guess what's going on with that tube but I surely know enough to commend you for not continuing to use it. I wouldn't use it again unless you can get someone with a solid electrical background to look at it and possibly do some heavy modding. It sucks when that happens, but it happens.
For the most part, I stay away from tube mechs. The builds I usually like putting on unregulated mods either sort of push it with one battery or else are completely unacceptable for a tube, and being that's the case it's not worth shelling out a ton for a single-18650 mechanical and then have to build higher than I really want. There are probably? some reasonably priced authentic tubes but a lot are pretty expensive for what you're really getting and I never do clone devices, for exactly the reasons outlined above. I have a complicated relationship with clones as many people do and certainly some people have well-loved and absolutely functional (if not wonderful) clone devices... I just don't ever go that route for mods. Sometimes RDAs. ANYWAY, really sorry that happened and I hope you can either get it sorted or simply get something else so you can forget about that tube.
With the caveat that I only received it yesterday, I would highly recommend the Invader III. I absolutely love it so far. I'm not sure if it's psychological because it's so simple but I swear it hits more like a mech than a regulated device. It's not a mech, of course, but idk. It doesn't hit exactly like a mech but it doesn't seem to hit exactly like your typical regulated device, either. I've got a .3ohm dual clapton on there just past "II" which I believe puts it around 4.2-4.4 volts and and it's absolutely singing. It would be nice if numbers/marks on the potentiometer really meant anything, but eh. If you do get it, just FYI according to Vaping Bogan the roman numerals on the potentiometer are: I: 3.6V; II: 4.0V; III: 4.6V; IV: 5.4V; and V: 6.5V.
I can't remember if the Tesla Two [Sub Mod] had a floating 510 or spring loaded... at the time I only had two atomizers and the Twisted Messes was the main one I used, it has a fairly long pin. I know I mentioned this above but the TM fit pretty flush on the Tesla Two and I didn't feel like I was cranking it down but eventually the connector got stuck in a recessed position and now only fires with the Twisted Messes or a few other atomizers. That's the only thing I'm a tiny bit worried about with the Invader III (or most other Tesla Mods with spring-loaded connectors, frankly, including the Invader Mini) but hopefully the III has a sturdier connector and I know to be careful now.
So yeah, knowing that I can't speak yet to its longevity, I absolutely love the Invader III. It has some good heft to it, seems really well built for the price, does what it claims to do as far as I've seen and can tell, and has a hit that's kind of in between a regulated and mech, to me. It probably works best with RDAs and RTAs but a) it doesn't sound like that's a problem for you and b) I don't really see why it wouldn't work with some good subohm tanks but I just usually prefer to have more info/finer control with those.
Ed: Just FYI, the Invader III does seem to have a slightly short 510. Most of my atties don't screw all the way down and I'm not interested in cranking because of what happened with the II. Doesn't really bother me but worth nothing in case it bothers you.
.. my coils are perfect, well within the device and battery limits, deff has a good connection, and my batteries are almost brand new and fully charged.. somi have no clue..and now im sad all day...
