Hard to explain.
Let's say that I have this kind of shape made of backgrounds (yes, my artistic skills are comparable to Picasso)
Everything is attached to movable 1, including movables 2 and 3 (eyes are attached to 2 and 3, not 1)
I can move the eyes by moving movables 2 and 3, and I can move the entire shape by moving 1
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However, if I move 1, this is the outcome
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Movables 2 and 3 did move, but they didn't move the objects attached to them.
Not sure if this is a bug or not, but it does complicate things in my case.