Bizarre site behavior upgrading/waitlisting to F for a flight in March. Flight: CLE-IAH-SAN/SAN-IAH-CLE. Used the "Upgrade using miles" option to upgrade the outbound segments. System showed that CLE-IAH was Waitlist Only and IAH-SAN was available for upgrade. When I pushed the button to confirm my 15,000 mile purchase, I got an error message "please try later or contact the electronic support desk". When I went back in to check the reservation, I see CLE-IAH waitlisted. IAH-SAN cleared. Ok, good. Weird thing is the system displays the waitlisted portion as a "5th" flight, and there's a 5th tab in the Seat Selector for this 5th flight. If I try and go back to choose Upgrade options, it gets even weirder, repeating CLE-IAH IAH-CLE over and over dozens of times. I took screenshots but I guess this thread prevents image attachments?

The itinerary email confirmation I received after the 15,000 mile purchase appears correct with the correct classes of service.