I have had this happen on literally every K-Box I have, I have 5 of them, usually happens after about 6 months of use, a couple even less. I have actually fixed all of mine, and have not had anymore issues, but it is a tough fix to accomplish, but I have fixed mine by seating in a clear silicone bed. I Remove the top, then push out the wire and insulator, using one of the other suggested fixes, I have used the o-ring from one of the OCC coil, actually two of them, one in the grove it was in, and one below. I then using a large bore syringe, injected a bed of silicone at the bottom around the hole, I then pull the center post back thru carefully and use the base from an extra tank to lightly set and hold in place, not too tight,
I then fully encased the center lead and the center pin housing from the back in silicone, making sure it bonds to the other material, using a toothpick to lightly blend and distribute the sealant. This has worked on 4 of 5 that went bad, I have a 5th that actually is holding up very well.
oh additionally I have found this to be a good permanent fix to the 4 blinking light issue once I have them functioning properly.
I added a finned heat sink to each of my K-boxes, 22mm dia (google it) stainless steel, this is tightened to the box once you have the spring loaded pin fixed, then you are not having the tanks push on the pin, and eventually it pushes the silicone gaskets around and they short.
I attach the atty to the heat sink, it is built much better, has screw adjustment, and never remove from the box once tightened, there is no need to remove once you have verified good connection,
I actually tighten down till it bites a bit and makes it very hard to remove, even if you get the connection repaired with another method, I highly recommend adding the Stainless Steel heat sink (FastTech has them, get steel, the aluminum ones are very iffy on working connection, they do have black and blue in steel too, other sites have them also) to your K-boxes, then you are not connecting and disconnecting from the spring connection all the time, which goes bad after the tanks are removed and reconnected.
It gives the mod a nice look too, but since I have added these to my K-Boxes, I have had no more shorting issues from the pin.