Call CX Immediately! Do Not hesistate! I don't know if it is a bug but...

Last Month - Paid Reservation
I had an ex-TPE D waitlisted for another day. My itineries keeps saying waitlisted, but when I did a mock reservation on the days I wanted, I saw the D fare. I immediately called CX and get it changed from waitlist to confirmed.

Last May - Award Reservation
This is also not the only time it happened. Last May, I was waitlisted for an upgrade award, and when I checked the website, it shows availability, while my reservations shows waitlisted. I immediately called MP to get it confirmed.

It may be a POS thing for some cases, but I suggest you do a mock reservation to see if your desired fare class will come through on the dates you want.