30 minutes on 1k line, agent plus supervisor to CHANGE a seat

Really? How do they expect to run an airline when I can't change my seat online (well I can, but after I end the record it still shows the original seats). Then the 1k agent can't change it either ("I've had this happen before"), needs a supervisor. What a waste of 3 peoples time!

I had that happen on a flight where the aircraft was transitioning from no E+ seats to having E+ seats.

Nope, it was a flight in a few months with many seats available and I was simply trying to change one seat for another No change in aircraft, should have been simple

I can't begin to grasp what could cause that. I've had to call in to change seats (award F wouldn't let me select seats on line), and after 3 seconds on hold, it took about 2 minutes for them to assign seats

I wish you better luck in the future. It sounds like you got less than the "A" team.

Sounds crazy, but there has been a lot of that this year.
But, please keep in mind there is no "1K line" anymore, you just cut into the "regular line".

Something like it just happened to me recently but it was for a two-segment flight (HNL-LAX-JFK) that showed both segments as using a 757-200 plane, except that the second 757-200 was a p.s. (3 cabins), whereas the first feed-in flight was a 2-cabin 757-200. The mistake was that they had connected the two flights because they had the same flight #, although there was a plane change in LAX. I had to point out the difference in metal configurations, despite the identical flight #, to get them to split the flights, which then allowed me select upgrades and seats separately. Without that, I would select a seat on the second segment, log out, log back in, and it would show that I had not selected a seat.

Your situation may be happening because of a similar 'technicality.'

Had similar troubles (exit row seats kept changing to rear of an erj145). No E+, the exit rows were the best and they kept changing. Tried multiple times to change 'em back on line, it would take for a day, then gone.

Called "premier line" several times - given various stories - equipment change (not!), FAM (do they sit in the middle of the plane?) - managed to get the seats back, but it felt like a constant battle. At T-24, my seat assignments on .bomb were off, but phone agent assured me I was in the exit row, which I was.

On AA, the only changing of seats I've had to worry about is picking new ones when the upgrades clear, usually 4 days in advance, so I guess this problem is going away.

Yup, that's been my experience on AA too Not to mention that their phone agents speak and understand English (and are polite and professional).
This was the second time I've had to call for a seat change on this itin. and the first time it also took forever - neither agent had any idea why it was so hard but both mentioned it's been happening intermittently (?another SHARES bug)