Barry got it right: GDL scripts contains the name of macros, and when you save an object then AC looks for that by it’s name, and saves the macro’s GUID to the caller object. If you have more than one macros loaded with the same name, then the behaviour will be unpredictable: AC will use the first object with the name – and store it’s GUID to the caller. And yes, it can change save by save, depending on million things.
So the proper way of developing any libraries is to do not have duplicate names with libparts/macros loaded together…
Team Leader, Library Team