Uncanniness is mostly about misrecognition, bound to familar concepts. Something that is familiar to us will get processed lazily by our brains. We trust it in a certain sense. Things get uncanny when it is just at the tipping point of being a new thing that we understand as such and a familiar thing that we know. And because it is at a tipping point this can chaotically oscillate back and forth between familiar and unfamiliar within a short timespan. The resulting overlap of emotions feels "spookier" than a unfamiliar thing alone would feel.