Hey David,
Those Objects are not Duplicates! They are Linked!
If you Delete the Object (‘original’), the Link gets lost to, because there is no longer something to link to….
This is more or less what I wanted you to do, by advising to try this in a simple file.
If you stand before a mirror, there is you and your mirror image; if you remove the mirror, you will still be there, but the mirror image is gone. If you leave the mirror, but go away yourself, your mirror image and you will both be gone.
So, Delete the other Collection; not the one with the links.
If you don’t remember which were the originals, just Delete one Object and see if the other gets Deleted as well.
