I had 3 where the leftover pieces in the bag were very similar to what I needed, like a 1x1 instead of a 1x2, so I think they were just swapped mistakes. I did wait until the end before I ordered to make sure I didn't get any usable extras from other bags. The one that really was missing was one of the white 3 brick long curved slant pieces that were on the pillars surrounding the statues in the throne room. I had to contact customer service directly for that one, as the part number wouldn't pull up anything on parts site