A few weeks ago on second leg of connecting flight (ORD-DCA) one of our two RPU-confirmed-in-advance upgrades was downgraded (1K moved to new F seat; companion no coach seat). Flight booked full. Offered $300 downgrade compensation for one person or $300 each to take next flight, with seats for both in F. Took the latter.
(Still a bit puzzled as to how two confirmed seat assignments disappeared, but assume a pair of GSes misconnected or paid for those seats).