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Head tube concentricity problem

I recently bought a new gravel bike and when I got it home I noticed that the gears were not indexing properly so I made some adjustments. When riding down the street to check it out I also noticed that the headset was loose, so I tensioned it and all was well. Not wanting to ride a new bike in grotty winter conditions I put the bike in my garage. A couple of weeks later I noticed that the bearing top cap was not concentric to the head tube.  Despite dismantling the headset and reassembling it I cannot get the top cap to sit concentric to the head tube. Interestingly the compression ring is made from green plastic and not alloy as I have seen on other headsets. The head tube and top cap are both 46mm in diameter and should be concentric, but the top cap is off centre by just under 0.5mm. This exposes a crescent of the machined top face of the head tube on one side, and leaves the top cap over hanging at the other. The steering turns without any tight spots but it just looks wrong. Not being concentric I think that the seal on the bottom of the top cap cannot be fully effective and will in time cause a problem. Do I need to be concerned about this? Is there anything I can do to overcome the problem?

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