I have a credit from a cancelled, partially used round-trip domestic itinerary (PDX to the East Coast). There _is_ a change fee waiver on the ticket. I'm attempting to apply the remaining value of the ticket to a new domestic itinerary from PDX to Hawaii. The ua.com website was throwing errors so I called reservations and they handed me off to web support. Web support eventually said I can't use the value of a "one-way" trip for a round-trip. I can't find anything in the fare rules about that though. I suspect what is screwing up ticketing is the HA codeshare segment. But I haven't encountered this particular problem before either. Is the agent actually correct that you can't apply a partially used itinerary to a new round-trip?