If you're removing spacers, then you likely have too much steerer for what you're trying to clamp up -- the top cap is bottoming out on the steerer before it clamps the stem down to the headset. Add a spacer back in there (above the stem) and see of those gaps disappear.

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Some are born to move the world to live their fantasies...

https://triomultisport.com/
http://www.mjolnircycles.com/

Along the same lines as what briders said. The top cap bolt is used to adjust the tension/play in the headset. You make the adjustments while the stem bolts are loose.

Upon further reading, I'm wondering how you could have worked in a bike shop and not have the answer be obvious. Besides the butchered vocabulary... Hair width space between spacer and head tube? There should be bearings between there. Handlebars? Those don't even factor into this issue. How about a picture?

If you have indeed removed a spacer and not shortened the steerer, then that is your problem right there. Put the spacer back in (whether you move if from under the stem to over is immaterial), re-tension the stack-up with the top cap bolt, then tighten the stem bolts.

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Some are born to move the world to live their fantasies...

https://triomultisport.com/
http://www.mjolnircycles.com/

And before you ride the bike again, engage the front brakes and rock the bike forward and backwards. If you have movement/play in the fork/steerer, etc at all, please don't ride the bike and make sure you've got enough spacers to that the compression plug has effectively pre-loaded the whole thing, and/or that you really tighten down the stem bolts AFTER tightening the compression plug (assuming carbon steerer).