It would have been awesome if that ISBN issue were an actual ISBN re-use issue. I've run into issues coupling my system's design to the assumption that ISBNs uniquely identify a single edition of a single book. The intent of ISBNs are to be unique, but mistakes are made and resellers lose track or straight up abuse some ISBNs.
Not just that but when ISBNs were first introduced, it was common thought that they were used for cash register price scanning rather than computer-controlled inventory, so a number of early books had ISBNs re-used by publishers and it wasn't caught because they were meant to be the same price. These days you often see two barcodes on books, one is the ISBN and the other is the price.