Kangertech Subtank Mini problems, fixable?

So I've had the tank since June, and last week I'd been using my RBA just fine, but the last time I tried to change the cotton it burned way too fast and shorted the battery. I didn't have any replacement coils left for the RBA so I used some old coils and then ordered a pack of .5Ω OCC coils.
Most of the time they've been okay. I wiped out the chamber and everything that normally comes into contact with the battery so it's not been shorting. But the resistance has been pretty erratic and randomly fluctuates into the 2-3Ω range, but I can usually give it a minute to relax and turn down the wattage and it's goes back to normal. This is how it's been acting with both the new and the old coils.
But just now it shot up to 6-7Ω and I got way more vapor than I expected out of that hit and now I'm getting Check Atomizer errors and the resistance just reads in as -.--Ω.
I've screwed it in tightly to make sure the signal is okay but it's still not registering. I know it's a genuine coil too cause I authenticated the code on kanger's website. Is this coil just shot? And does it sound like it's the tank's fault that this keeps happening? If so is it fixable or does it sound like I need a new tank? any advice would be appreciated cause I'm depending on my fiance's ecig at the moment

(btw if it helps my battery is an Innokin Cool Fire IV that has been generally fine with my sub-ohm habits.)

 

I actually just switched my tank with my fiance's and my tank is still acting up on his battery (he has the same kind) and his tank is okay on my battery so looks like the problem is the tank. I even switched in a new coil (not RBA) and it didn't make a difference

 

I'm familiar with the first issue from my RBA but now I'm using full replacement coils and I don't see any screws on those (unless I'm somehow missing them). I think it must be a tank problem anyway since it's doing the same thing with a fresh coil.
Also I'm not completely clear on which pin you're talking about. Do you mean the base with the adjustable airflow, or the pin on the bottom of the coil?