I can't speak on the mini, but I have a Subtank (original version) that has seeped juice since day one. I have tried changing the o-rings repeatedly, but it still weeps at the base. It provides a good vape, but just can't get past the constant seeping.
How do you vape? Mouth to lung (MTL)? If you see vapor coming out of the air holes whenever you vape, it is probably condensation. The generic way is to hold your vape upside down and blow up with paper towel covering the air holes or something and have your eyes closed in case juice gets in your eyes (it burns like hell I am told).
Depending on your Subtank and you have two air holes, you can blow in one and have a paper towel over the one pointed down and that works well too. If it is upright and you blow into your drip tip, all of your juice will just empty out.
If this isn't it... well I rarely use the OCC coils. Mostly the RBA part. I have two originals, three Minis, and three Subtanks Plus and I purchased the newer RBAs with the big holes for the Minis and the Plus (won't fit in the originals, or will it?). And the rare times I have used the OCC coils, some leak. If you see tiny bubbles streaming to the top, that is usually the OCC seal leaking.
The only other leaks I had with the RBA part and I am sure it would happen with the OCC too, is if you burn the cotton in half (at the point of the most heat). If it burns slowly, you won't even taste it and everything seems fine. But it is now leak city. Even just vaping or not and it just drips to the bottom and floods everything. I lost 7ml this way while I slept.
Sorry if I made all of this sound horrible. But it isn't really. I had to learn all of this and what to look out for and the only leaks I get nowadays is occasional condensation. And the worse that can do is like 3 to 4 drops if you do nothing about it. I vape MTL most of the time and that is the worse for condensation. And I chain vape too and once every few hours clearing it is all that is needed.
