Since "new_child" is inserted at least into a new place, it needs to be removed from its old place as well, so that part seems correct. The problem description does not make it clear whether or not "old_child" is handled correctly, but looking at the code (and lacking a complete example that shows an error), I cannot see anything wrong there.

I'll close this ticket since it has been idle for years and it is unclear to me from the description whether it is an actual misbehaviour or a misunderstanding of correct behaviour.