Question is.. is it seeping or is it leaking, or is it condensation. With the stock coils and the "exotic" coils, they cool down is slow and it continues to cook juice after releasing the fire button. So I get a decent amount of condensation, and that is not a big deal to me. It is the coil's fault, not the tank.
I finally got my tank to leak on me. And here was how. I usually run my tank almost dry, that includes tilting to see how much juice I have under the deck. I run it until I can feel it no longer wicking and I get a dry hit. So that is when I fill. The other day, I filled when the juice has just at the bottom of the glass. I then let it sit for a while before I vaped, and that was when I saw juice in the air flow hole.
So with that, I think that if you are not running low on juice, the suction caused by opening the top cap can pull and flood juice in the deck, causing it to run into the air flow.