CX198 is also "
sold" as AY5102, BA4550 QR5811 and some other non OW airlines.
At times OW codeshares can have different D fare class availability.
Also ff earning can vary with marketing carrier.
A real live breathing
Travel Agent or
skilled~knowledgeable airline phone agent can sometimes get around the bugs in the OW software.
Edit
https://www.flightaware.com/live/flight/BAW4550