Opal says, for instance, when she was little she and her parents went to a village in Peru to retrieve an old cursed ring that was causing a lot of... problems. And even though whoever was wearing the ring inevitably ended up mad and so on, a new Muggle kept wearing it whenever the previous owner ended up deposed. They just couldn't make the connection. Her mother said it went through more than twenty different owners in the space of a year before they liberated it from them.