Sorry, but it all comes down to wicking. The device itself has nothing to do with it, given that you've actually tightened the drip tip adapter down properly after inserting the tank. The boro tank can be a problem if the seals are trashed (o-rings top and bottom, as well as the glass gasket), but that's easy to spot and fix. (It's worth picking up spares packs while they're there and cheap - the gen-you-wine article carries a stupid-high price because it can, and you can get five of the SXK kits for the price of a single Billet Box Vapors kit, and the bottle in the BB kit isn't that good.)

Apart from that, it's straight-up wicking. Admittedly, that's easier if you like a tighter draw - with most rebuildable boro atties, you can be awfully generous with the cotton before it even thinks about dry hitting if your draw is tight. With a looser draw, you just have to gradualy up the cotton until you hit the balance point, and in some cases may need to use a larger coil, depending on the atty. I've never leaked a drop with my BBs. There are some atties that are better at preventing condensation around the boro than others, and condensation plugs are worth the bother if you're using the boro tank, but condensation isn't leaking. Even the sort-of-Kanger RBA that comes with the BB is well-behaved if you wick it right, and that's with 50/50 and 60% PG juices.