It looks to me as though the top cap (regardless of how it fits cosmeticly) is bottomed out on the steerer end/top of plug. If so then the function of drawing up the bearings will not fully happen, a loose headset bearing results. Adding one more thin spacer (maybe a couple/three mms thick) under the stem will raise the stem's top surface above that of the steerer/plug. Then the cap will seat fully on the stem and the bolt will draw up the steerer completely. Andy