A friend of mine is having a leakage issue with her Kanger sub tank mini. It is leaking around the air holes. She closes the valves when she fills up the tank but it always leaks. She has replaced coils, orings but it still leaks quite a bit. She was told she needed thicker juice so she corrected that but it still leaks. I am too much of a noob to figure this out so I pose the problem to you guys....could it just be a bad tank?