I have now had issues with the upgrade list on every itinerary this year that wasn't in paid F. (Though, most flights have been in paid F.)

For a flight tomorrow, I was upgraded to C+ at the window for the first leg. For the second leg, I am only showing on the list for F, although the itinerary clearly shows a C+ upgrade requested. I asked via messaging and was first told the issue was that the flight was oversold (even though there are 20+ seats available?). Next I was told I was added to the list. When I sent a screenshot showing I was still not on the list, I was told I was actually #X on the list (which was my position on the F list in the screenshot I sent).

I had a similar issue in January. I have also seen other posts about similar issues.

Are others having issues? Am I just unlucky? Has someone decided this is a good way to further increase the percentage of flights I am buying in F?