You either try to take it apart and fix it for yourself or you contact VS support. I suggest contacting the VS support since they are a pleasure to work with and they will surely help you. As for the connection issue with a Subtank: I also had that, but it was the only atomizer that gave me those issues. As far as the fire button goes: sadly, from time to time, I also have the same problem with the fire button.
I also had some resistance reading issues with my Vaporshark and after exchanging some emails with Vaporshark, they asked me to send the device to them for repair. I suggest you have a talk with them directly. PS: I can keep you updated on how long shipping+repair takes, if you want.