A coworker had a surprise when he was working on a copy of another document. He opened a drawing and the part it referenced. Saved a copy of both part and drawing. Closed original part and drawing. opened copies, deleted all but 3 configurations and edited feature. saved. opened originals and surprise! the feature was edited exactly as the copy was, but all configurations are present... Is that possible? Can editing one part ever edit another part in a separate file? Can you link two part files?
I would expect there was user error in the save-as operation. check the file references in the new drawing...