I just unscrewed my Aspire Atlantis 2 tank to refill and the coil is stuck in the upper part of the tank. It's a new coil, so I wouldn't think it was gunked up from juice. I refilled with it in there, screwed it all back together and it's vaping just fine, but still won't stay screwed into the base of the tank when I opened it again. How do I keep this from happening?