Background: I bought a 'Pake C'mute' frameset a few months ago and started putting it together after moving. I had enough tools to put most things together, but nothing to install a (threadless) headset, so I let a local shop do the whole shebang (press the cups, cut the steerer) and assembled the bike.
After riding for a day or two, the headset felt a little loose, so I took to the wonderful folks at a bike co-op on the way home and we tightened up the headset. Everything great, right?
Well today I noticed that there was a significant gap between the bearing cap and the bearing cup I did some searching on here and elsewhere online and found that other people had noticed some peculiarities with their FSA headsets, but I wanted to investigate further...
I pulled it apart and noticed that the split ring doesn't want to sit in flush... one edge wants to sit higher than the other. When the bearing cap goes down, it does the same thing. The cap toward the frame side (back of the bike) has ~1.0mm of gap between itself at the cup, while the front side has 0.55mm of gap.
What could be the problem? Steerer isn't bent (problem remains the same as the steerer is turned), so I'm guessing since the cup looks fully seated that the head tube wasn't square to begin with, or it was faced improperly.