Erasmus

I apologize if this has been answered before; I was not able to find it by searching.

I have an AA-plated (001) ticket for CX metal with a CX flight number (i.e., NOT a codeshare). I would like to upgrade K to U (no premium economy on this flight) using Asia Miles. I have received many conflicting responses from Asia Miles about whether this is possible. Should it be? If so, in advance? Or only at the airport using an instant upgrade?

My story:

I recently tried to upgrade NRT-HKG return. On my first call, everything seemed fine, and they wait-listed me for the upgrade (quoting 30K miles for the return, as expected). The outbound cleared, so I called to redeem. They queued it for ticketing. It never ticketed. Day of departure from LAX (I was flying LAX-NRT on AA) I spoke with an AAgent in the Flagship lounge who called CX. They were told it was not possible to process the upgrade. Dumbfounded, I insisted it must be because they were happy to deduct miles and dispatch for ticketing; it just hadn't been handled yet. They said they'd work on it.

When I arrived in NRT, I checked in at the CX lounge, and everything seemed fine: ticket was issued, (17.5K) miles deducted, etc. I flew in my upgraded seat, not thinking anything was amiss.

Now, my return has cleared. I called to have the additional 12.5K miles deducted and the ticket reissued. First, they said it would cost 17.5K miles again. Then, they changed their mind and said it was not possible at all since it was an AA ticket. I pointed out I had just flown in on the same ticket, and they claimed they have no record of my outbound upgrade (indeed, the CX reservation on the website has me back in K from U on the outbound, which it was in before and shortly after I flew). Huh?

So, did I get lucky with somebody making magic happen on the outbound? Was it processed as an instant upgrade? Or am I getting bad information? Just wondering how hard to fight/what to push for when I try to depart HKG. My record currently shows me holding both a confirmed K and U seat, but the miles have not been deducted, so I presume the ticket not (yet) reissued.