Hi,

I can't see what a spacer for a threadless headset
has to do with a threaded headset, or what the
adjustment of the headset has to do with the issue.

As others have said, they shouldn't normally move,
but should move rather than break in a tumble.

rgds, sreten.

Several reviews mention the quill doesn't seem
to tighten enough, you might need to be creative.