Weird one this. Just been speaking to the op on another thread. I suggested the same as crusty. Back the pin out a touch in case of poor contact.
I've had four of these and apart from the dribble from the 510 on the first they've been spot on and I use two as daily drivers.
Just put two 0.2 ohm builds in different rda' s on the two I use daily and they are reading spot on. Exactly the same as the coolfire and .01 off from the DNA board so pretty good for sub £30.
Not unusual to have a janky mod at any price so may be worth swaping with the guarantee if the 510 trick doesnt work.