Kind of reminds me of the old gent who kept putting dollars into a change machine and cackled every time the change came out. It turned out that the machine was dispensing five quarters for each dollar inserted. Now THAT is a nice, quick return on an investment!
Yeah, there's a guy on Youtube with a video of his 2018 Silver reverse proof set with an extra quarter in it. seems to happen, although I don't think frequently. His looks like it damaged the coins though the way they are stacked in there.