completely baffled

[efinch]

So I got a dbox puritank from ft today. Cleaned it out stuck a head in primed, filled waited vaped. Horrible burnt rubbery taste, so I removed the flavour wicks, same problem. Put 3 different protank and t3s heads in that I'm currently using on other tanks, same horrible taste. Put in heads that I've recoiled with cotton that I know work on other tanks. Same problem. Checked the air holes and they're not blocked. Checked the o ring to see if that was the problem but it's not. So it's got to be an airflow problem so loosened the base a little, didn't screw it down all the way. Same problem. Screwed on the base of my protank instead, problem solved. Any one else experienced this? It has me scratching my head