I just received a brand new EAI 18t track cog from Ben's cycle. It's for my Campy Nuevo Record track hub. The problem is that it only goes half way in and then gets stuck. I've compared with the 14t Campy cog that originally was on and that spins on smoothly all the way. What's wrong here? I know cog threading is (almost) universal so where's the problem?

The EAI campy lockring works fine by the way.

Should I force the new EAI cog on from the halfway position or do I risk breaking the threading then?