Could be a number of things but looking at your coils 70 watts should be more than enough to vaporize the liquid. Have you only had this happen on the 1 coil? Or has it happened after you change your coil?
If changing the coil doesn't fix it - sounds like the coil is flooding which can be caused by a coil not being seated properly or you could be drawing too hard / fast for your coil to vapourize all the liquid in the coil. Try taking slower draws and see if that helps?
I had the same issue - for me the cause was using a narrow bore drip tip on a U-force tank. It meant I was pulling through too much liquid. As soon as i changed back to the stock wide bore drip tip, the problem disappeared!
