Originally Posted by
donotblink
Lately, I've noticed the mobile app allows seat changes even when the website doesn't. Give that a try. I'm not sure if they automatically reissue or not, it depends on what type of change was made, if the change impacts connecting airports, they will reissue, but if it's just the time, they won't.
Just a quick update: my late-May DFW-LHR flight departure moved up 25 minutes earlier. Nothing else changed apparently. After a day and half, the seat map opened back up and everything was still the same.