I think my A2 had the same problem (sometimes a short, sometimes it worked fine, sometimes no connection at all) and I took the bottom part apart. It is quite easy self-repairable, you need a
new connector and some hot glue, a solder station and spare wire.
The hot glue is used to isolate and fixate the positive screw in the base, there are better solutions to fix it but I just rebuild it like it was.
I drilled the connector away (a small ring remained), removed all that hot glue that is inside of the base. Then you can remove the two screws where you fix the wire.
Now I was able to push the rest of the connector out of the base with a screwdriver (I think I used a hammer very carefully).
Now fix the wire if damaged, put the screws back in place. Apply hot glue again and resolder the wires to the connector.
Finally you have to press the connector back into the base (add a steel adapter like 510/510 or 510/eGo to avoid damage to the connector).
Good luck and maybe you can take some pictures (I forgot to do it)!
