A few months ago, I had a similar issue where the add/collect was materially different within a few minutes. As it turns out, the system bumped me out of first class on a segment that wasn't being changed. The web site had showed no indication that this was happening as it only showed the segments being changed. Had I not gone back in to verify the reservation, I'd likely not have noticed for several weeks. I called right away and, after an hour on the phone, AA was able to rebuild the reservation back to what it should have been. I'm not saying this is what happened here or that anything actually went wrong -- just recommending you double check the classes of service, dates of travel, etc.