Unwanted bone movemnt in AimOffset/BlendSpace

I’m trying to use some Aim Offsets to my character. The thing is, that some of the bones ( actually all the last ones / the deepest ones in the tree ) get some unwanted movement, but none of those bones have position animation. It’s just when I blend in-between the nodes, the starting nod’s position is fine, then the bones get some unwanted offset between the nodes, and finally, in the other node it’s still in the same position as in the first one. Any ideas why does it happen?