Ah i'm with you now. Went back and read properly...
Your problem is with the inner chamber not sealing on the deck. I measured mine and there is a 0.2mm clearance between the inner chamber and the deck. Will be interesting to hear what yours measure...? The inner chamber overlaps the deck to the top of the air holes. I agree, they could've put an o ring there, but that would've complicated putting on the top cap more. Its kinda fiddly already putting on the top cap. The inner chamber can hug the deck if the top cap is held just a little scew, when replaced. That gap i'm sure isn't a fault. Its by design. That is where the air came from when you blocked the air holes.
Here is my theory on how the airflow works in there...
As i see it, when its in operation, liquid and condensation builds up in that gap. Its very minute. Only 0.1mm per side. That liquid/condensation seals the air escaping back through there, so the air follows the easier route through the channels. When its dry inside the chambers though, some air will escape through that gap, but not much, as air takes the route of least resistance. The route through the air channels is the better route to travel.
The reason you get a harsh throat hit is definitely air related. Have you played around with coil placement? I see the two air outlet channels at the coil, aren't at the same angle. Have you noticed that? Maybe the air don't hit your coil well to cool it down...?
The reason i say the gap is sealed by the liquid/condensation, is if i remove the top cap, after a good vape session, i can see the top of the deck is shiny/wet where the seal was broken...if you know what i mean...
