Hi, thanks so much for taking the time to look into this. You're file absolutely works and I tried reproducing it with a bit more complexe rig and it also worked.
Created kind of a 2 leg rig, with a ctrl for the root and the position.
Put a sphere in the middle of the 2 legs that is skinned to both foot.
Then a cluster on that sphere. that I grouped and put under the root ctrl. relative mode activated. cluster input moved benith skincluster on the sphere
created a ctrl for the cluster, put it into a grp same pivot as cluster.
poly point constraint the group of the controle to a vertex of the sphere (so that it moves with it when rig moves)
put the group under the root also
and connected translate rotate and scale of the control to the cluster via node editor.
it works fine, even when I mode root, leg or whatever in translate, rotate and scale.
buuuuuut I went and redid it into my rig and it doesn't! haha
So I attached my rig and it would be really amazing if you could explain why it doesn't work 😞
on the image I circled all my clusters, but the one marked 1 is the one I completely redid as the same way I explained. The other ones are with my different workflow (that still doesn't work hahahaha)
There's also the simpler rig that works.
I'm really grateful for your time 🙏
P.S: oh yeah and the global ctrl is scaled down to 0.027 that's 'normal' because I realized after ward that my character wasn't really much too big for my sets... And the clusters didn't work well with scaling that much so did them on the scaled version directly... I really hope that's not why it's not working properly though... 😮