To add further credence to system issues, I was trying to change a mileage ticket to Europe yesterday. The outbound remaining the same, only the return changing. The day I wanted to travel, only main cabin was available, so with the new itinerary, I should have been receiving 40k miles back (70k one way Delta One-30k one way main cabin). The agent kept insisting that I needed to pay an additional 117k miles for the new ticket, until a supervisor looked at it and agreed something was amiss.