If the spacers are loose, there's no way that you're compressing them to establish preload. The system is pretty straight forward. the top cap bolt pulls up on the star nut or expander, and pushed the cap down, which in turn pushes the stem and spacer stack down onto the centering cone securing the headset against the steerer and compressing it to get preload.

As a result the spacer stack is under the same amount of compression as the headset bearing, so slack spacers means slack headset. Find out why you cannot compress the spacer stack. reasons include, in order of commonality

1- stem tight and won't slide down freely --- loosen stem bolts
2- top cap beaching on top of steerer rather them top of stack --- add spacers
3- expander plug sliding up and not serving as a fulcrum for the screw --- tighten plug, and or add traction compound to the plug
4- top cap running out of thread and not able to screw in far enough to compress stack --- shorter screw, or push plug in deeper
5- undersized spacer in the stack binding and not sliding freely --- replace or deburr spacer as needed, identify as one with tight spacers above and loose spacers below.

From your description of prior efforts, I'm leaning to #4, but do a complete review. You're missing something obvious, and I doubt it's a headset problem. If the spacer stack is tight and the headset loose, than it might be headset related, inverted bearing, missing internal spacer, etc.