I haven't caught up with this thread yet but I have a question.
I got a Zenith V2 rda this weekend but it will not thread all the way on my Paps SSv3 or Lux V3 510. It will not thread all the way on my friends Lux V3 either. But it will thread onto the Paps X top cap 510. Is there really a difference between the v3 510 threading and the X?
No, there is no threading difference in the 510 portion. First, are you using AW IMR? Check your GPins and report back if they are the long or short.