Had some interesting issues with SDC last week. Wife and I were flying LAS - DFW on an early evening departure. When I woke up our flight was already showing a delay which got worse as the morning progressed so I did a SDC to an earlier flight.
When I did the SDC it split the PNR so I ended up with new record locator, but my wife stayed on the original. Never had that happen before. However, we appeared as #1 and #2 on the Standby list.
The delay worsened to the point that the app had the notice stating we could change flights for free. So we changed to the same flight that we'd done the SDC for and had confirmed seats on that flight: 14E and 14F. We downloaded BPs for these seats. However, we still appeared at the top of the Standby list.
Before we left for the airport 8A and 8B opened up (MCE instead of just Preferred) so we moved there. However, we couldn't get BPs for these seats - we could only get 14E and 14F. At the airport the check-in agent issued us paper BPs for 8A and 8B but couldn't get us off the standby list and asked us if we could do it ourselves (which I don't think we can do but, if I am honest, she didn't seem to even want to try to do it).
Our standby then cleared (even though we were by now confirmed on the flight we'd done an earlier SDC to) - so we had paper BPs for 8A and 8B plus 28A and 28B if we tried to download them in the AA app. I spoke to the GA when the gate opened and she was able to get the duplicates removed, leaving us in 8A and 8B. She didn't know why we'd ended up both confirmed and on standby but she was appreciative of us coming forward as it allowed two additional standby passengers to travel, stopped any last minute manifest reconciliation issues, and prevented any IT hiccups meaning we were incorrectly shown as a no-show and had the other flights in the itinerary cancelled.
So I suppose I am just curious as to whether anyone else has had the PNR split when doing a SDC via the app, and whether anyone has been both confirmed and standby on the same flight in the same cabin?