Assuming you got the correct heads for your PT, if you look at the 510 connector end you will see there isn't a lot of clearance or difference between the height of the 510 threads and the base of the coil extending longer than the 510 threading. It is or should be proud of the 510 threading - but just barely. The only time I've had a problem like you describe was when a coil wasn't fully screwed into the PT base, so the center of the coil wasn't making contact with the center post on the battery. Try backing off the coil a bit and screwing it down onto the PT base again.
If that doesn't work, there is a chance that too much fiddling - screwing things on harder and harder to "fix" the problem - has pushed the center post of the battery down. You could be at the point where the 510 threading on the PT is now making contact with both the threading and the center post of the battery, causing a short. You will need to pull the center post of the battery up a bit to correct that.