Originally Posted by number_6

The problem might be LAN Peru; I don't know the current rules, but some of the LAN (formerly LAN Chile) group airlines are excluded from OWE travel (they are treated as a codeshare and not part of Oneworld, even though LAN has a controlling interest). Thus some LA coded flights are not allowed to be used on a OWE; that might be the restriction you are running into, and not going through the same city multiple times (which is allowed). You might have to hub via SCL to get allowed flights. Probably LAN would be best able to tell you which flights are currently allowed, as they control this (unfortunately dealing with LAN on anything is difficult at best).