channa, I was under the impression that even though EUA might 'choke' due to an 'out-of-sync' reservation, the system simply stops upgrading passengers at this point—or until the issue is resolved. I know for one that last year I had a messed up ticket, and the agent said that I was probably the reason why EUA hadn't run (because the system simply stopped rather than skip over me).

Is my understand of the system correct?

Thanks!