DL agents often don't know how to get MU (China Eastern) award flights properly. I once called back 7 times - yes, seven! - but all along they had the MU flight in the wrong fare class, so it was not coming back as "confirmed" and was just waitlisted for over a week. All it took was one competent pm-NW agent to rebook it into the proper fare class for MU (alas, now I forgot what it was) and it came back as confirmed in a few seconds, and was all set and ticketed.
So, make sure that you get a competent DL phone agent and ask them are they sure, really double, triple sure, that they are booking it / querying into the right fare class (ask them what it is, see how many different fare classes you are told each time you call - then when so, ask them, "but the other agent said it has to be fare class __, so what is it really?" and perhaps then they'll check and confirm).