You may be talking about my post, as I posted about this same thing last year. I only use the rattling shells to check POA/POI at 10 yards, as I do not trust them out to 40. I am sure there is nothing wrong with them, and they would pattern just as well as non-rattling shells, but I prefer the shells that are put together the way they are meant to be.
My guess is that some of the resin just got knocked loose somewhere between the factory and the store. I would just try a few at 40 and if you are happy with the pattern, keep them.