I think there's a lot of inexperienced/newbie/poorly-trained agents out there these days, including those that aren't well-versed in dealing with GGU's. I've been running into more and more complications modifying reservations booked with GGU's. Modifications which in the past have taken just a few minutes to process are now stumping agents I've dealt with recently.

For example, for a September HNL-SEA flight I originally booked back in June and to which I applied GGU's for my wife and myself, I wanted to change the flight to depart a day later and from OGG instead. The new flight had U space available, so from past experience, I figured it should be a simple matter to call in and change to the new flight and secure the upgrade by "transferring" (for lack of a better term) the GGU's to the new flight. But the first agent I spoke with said the only way it could be done was if I had additional GGU's to use for the new flight and applied those, and then I could reach out to Customer Care and have them re-issue the GGU's for the original flight. But as I mentioned, I had done this type of "transfer" many times in the past (it's been my standard strategy for many years to preserve expiring GGU's by booking a future dummy flight with U space and then calling in weeks or months later to change to a different flight with U space). So I figured the agent must have been a newbie, and so I tried to HUCA, but the second agent I spoke with said pretty much the same thing. I didn't feel like continuing to play the HUCA game or risk the U space disappearing on me, so I just went ahead and did as they suggested, using other GGU's I had for the new flight and then calling in to Customer Care to have my original GGU's re-issued (though as an added bonus, the GGU's they re-issued to me won't expire until 12/31/2025 even though the original GGU's were set to expire at the end of this year).

Second example. For the same OGG-SEA flight, about a week after I made the change I just described, I noticed that the underlying N fare had dropped by $40. So I tried calling in and requesting a price adjustment with the difference refunded to me as wallet credit, while stressing that I wanted to ensure that my upgrade was preserved (there was no longer U space available for the flight). Again, I've done this type of price adjustment for GGU-applied flights many times in the past without issue. But this time, they claimed that in order to perform the price adjustment, my existing reservation would have to be cancelled and a new one would be made. And because my reservation needed to be cancelled, there was a risk I would lose the upgrade if the cancelled flight didn't result in the U space being returned. So I thanked the agent and dropped the call, intending to play the HUCA game again. I waited a few hours and called in once more, but again, got pretty much the same response. So I slept on it and called in yet again the next day, and the agent initially indicated the same thing, but asked me to hang on while they checked on something. After a few minutes, she came back and said she was able to successfully do what I wanted, except rather than issuing wallet credit, she had to issue me credit certificates instead, which was perfectly fine with me (I later simply deposited the certificates into my wallet). Maybe I should have probed more to try to understand what exactly she ended up doing and what I should ask in the future if I ever wanted to perform a similar price adjustment again, but I didn't.

So I don't know what the deal is, but at least in my experience, it appears to be getting harder and harder to make changes to GGU-applied flights while still preserving your upgrade, even though such changes were trivial in the past. HUCA may or may not help.