If the
coils are intact when you remove them, I'm guessing you're having a short circuit, and the mod is shutting off.
I don't want to say I've mastered it, but I've become very good at rebuilding the Protank 2 I have. I have zero leaks or gurgles, and I find it's performing fantastically at 13 watts.
What I have found is, if you don't clip the leads right, the ground side can poke through the rubber insulator and contact the center positive pin. So let me ask, how are you trimming the excess coil lead after you insert the insulator and center pin?
What type of coil are you building? Microcoils? If so, are you heating the coil after you wrap it, and pinching it to remove gaps and oxidize? If not, the resistance may be changing dramatically as you use it. Dry burning the coil in the head isn't recommended, but you can gently pinch it together with tweezers and torch it 'till it glows for a similar effect.