Years ago when I had to modify HKG-NRT-IAD which was on NH and UA the check in agent at HKG couldn't get it to reissue. Got close to check in close so the manager told the agent to FIM it, which I think is a way to show you have a ticket but unfinalized. Apologies if I'm getting the terminology wrong. Not sure if they still do it, but maybe bring it up if the ticket is stubborn.