The dual coil design has some flaws. I use a high VG juice and this may be the cause, but the coil burns out so quick because it does not draw enough juice to the middle bit, making it burn out often.
Never had an issue like this with the HW-M setup.

You have not fullfilled my order as i have not received my order as yet !!

Eleaf HW1, HW2, HW3, HW4 HW-M, HW-N Replacement Coils