I have a Chris King 1-1/8" NoThreadSet on one of my bikes. I'm running it with a tiny (maybe 2mm?) spacer on top of the stem, under the topcap.

It's a coupled travel bike, so I regularly remove the stem, spacers, & topcap for travel, and replace them just as regularly. Have done so for 2 years and never any problem.

Recently had to have some major frame damage repaired, which necessitated removing all the components. Since I don't have the tools to remove the headset, the framebuilder offered to remove, and subsequently replace that. He did so, and everything appears good as new, exactly as it was before the repair

...except that now, after I install the spacers, stem, & topcap, adjust the bearing preload to the correct torque, that little 2mm spacer between the topcap & stem rotates freely.

It never did before.

Everything seems to fit together correctly as before. As mentioned, I'm adjusting the bearing preload (topcap bolt) to the recommended torque, same as before. Stem bolts are tightened to correct torque, everything appears pushed down onto the steerer and/or headset as far as it will go. The topcap does not rotate...but the spacer in between the topcap and the stem does rotate, freely & easily, which it never did before.

Any ideas what might be causing this?

And...is this anything I need to worry about?

Thanks.