I was experiencing juice leaking from the air controls, but it would leak sometimes after a day, sometimes after a couple of days. However, I wasn't always closing my air flow prior to top filling.
I contacted Beyond Vapes, and they told me that they would send me a replacement, but that, at that time, they were out of stock.
After having the SB for a few days, I then made a conscious effort to ALWAYS close the air control, prior to top filling. After I filled the tank from the top, I would take a pull on it, with the air control closed, then open it up.
I went about five or six days with no leaks, and thought the problem was solved, but, alas.... it leaked again! Not nearly as bad as it was when I first got it... leaked very seldom, but still leaked.
Got the replacement SB, and used it for the first time yesterday.
Gotta say, I LOVE this tank! Easy to top fill, large capacity, great vapor flavor and production, GREAT looking....
Used it all day yesterday, and I mean ALL DAY, for the 1st time with the replacement tank. Late last night, as I'm getting home, I see some juice on my hand... not alot, about 4 or 5 drops, but the tank did leak. I do think I turned the tank at a sharp, 90 degree angle right before it leaked, but it still shouldn't leak.... my Kanger Sub mini never leaks!
My iSub tank is the same way... can go days working flawlessly, then suddenly I get juice coming out of the air flow.
Only thing I can tell you is, close the air flow completely, when you're on the move, as I don't think it will leak with it closed... it seems very tight when closed.
Second thing is, Beyond Vapes is a great company, and if you're really unhappy with it, or if you want to give it another try and see if a replacement works better, they'll take care of you! (Again, mine only leaks on VERY rare occasions, so perhaps you did get a bad one?) They have a phone number on their site, and even return calls in a timely manner and strive to help their customers!
Sorry I couldn't be more help!