First, glad I found the thread. I tried two heads and same result as a few here. I've had my rdna 40 since the first run so I am used to nickel builds and the difference.
I believe the problem to be poor wicking. Example, on my hobo, temp won't begin to kick in at all until my juice is needing to be dripped again, going dry. If it stays wet no protection unless of course I take so long of a pull that the wicking can't keep up.
Same for these heads. Prime it and it rocks @ 420 until it dries up. Juice is just not getting to my coils. Simple as that. No bubbles indicating flow, pulling the head and looking, there is just no juice. I am using a Kanger subtank mini. BTW regular OCC head plenty of tiny bubbles.
Is it possible for a vacuum condition on the subtank mini not to allow juice to flow naturally?