I just built up a new bike and for some reason or another, the headset seems like it wont seat properly. There is a small (<1mm) gap between the top headset cover and the headtube. The headset spins freely when I rotate it. When I rock the bike back and forth, you can feel the slight play. This is a carbon steerer, so I have an FSA compression plug in it, and tightening that doesnt fix anything. The race is seated flushly.

Anyone have any ideas? Its a threadless integrated headset, Campagnolo style, in case you're not familiar with the FSA Orbit CE.