This problem can also happen if:
- Coil leads get damaged by overtightened screws (or the screws have sharp edges).
- Atty lead holes have extra space, such that the lead screws down tight but does not make good electrical contact.
- Cotton threads are facing the wrong way (e.g. you cut the pad perpendicular to the fibers).
For best wicking with the flat cotton pads, I cut my strips about the same width as the inside diameter of the coil, then roll them to compress them to a point, like threading a needle. Applying juice will allow the cotton relax to its original form.
Drier/finer vapor can be achieved by cutting wider cotton strips (so it stays compressed more tightly in the coil), but stuff too much cotton in there and it won't wick properly.
Whatever width cotton strips I cut, I make sure to cut them all at the same time for consistency.