I suppose blending / blend spaces etc are just not for moving parts individually like that (but create an average). Odd I’ve never ran into this case 
I doubt I’ll be of help
Blend Spaces in Unreal Engine | Unreal Engine 5.5 Documentation | Epic Developer Community
You’d think each part gets some kind of its own local blend space between state A and B taking X as interpolation alpha, and that this alpha can be communicated between parts for their own local blend space properly. Just haven’t worked with animations enough to come up with a screenshot of that in the animation blueprint.