I've got two TfV8 Big baby beast tanks the one with the original coils and another one I made some SS Clapton dual coils for, both are using RBAs. The original one works fine the other has problems. I just took a good look and I find that the tank has some problems, depending on how you put it together you can get a shorted coil or you get a high resistance so the coil only draws less than one amp.
That's the problem I'm running into you press the fire button and it only draws less than 1 amp so you get no vapor. I tested out both tanks and can get the good tank to have the high resistance also.