I think it's just the how it works with the stack you have. Not everything works all the way up the stack. Sometimes you just have to collapse the stack and keep going. Make a backup of the stacked version but collapse a copy, drag your elements over and then delete the parts you don't want from the copy that copied too much. I think you just have to do a workaround on this one.
You could just 'Detach' the element you are trying to copy and then drag copy that detached mesh as many times as you want. Then reattach it later when you are done. That might be the easiest method.
Rob Holmes

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