I am looking at flights YYJ -> RSW (Fort Meyers) for Feb 2013, specifcally the 4th, but it is happening on multiple days I've checked. Booking for 3 px, in case it matters.

Flight option 1
AC190 - Upgrade available
AC1234 - Upgrade available

Option 2
AC190 - Upgrade NOT available
AC1236 - Upgrade NOT available

Option 3
AC190 - Upgrade NOT available
AC1232 - Upgrade NOT available

Option 4
AC8050 - Upgrade not available
AC116 - Upgrade Available
AC1236 - Upgrade Available
...

AC190 is sometimes availale sometimes not, AC1236 is sometimes available, sometimes not.
I can't post a screencap to show it, but it is very weird. Thinking about purchasing Latitude to upgrade, but I am not confident that the upgrades will succeed with these flakey results.
Anyone else experience this?