I had this same nonsense from Cathay a few times.
In my case the middle name shows up everywhere... except apparently when trying to do OLCI.
I recently flew F from ORD to HKG on a partner award ticket. OLCI failed. I called MPC, and the agent scared me by saying there was some mismatch and maybe I would not be allowed to fly! I've flown so many CX segments using this same online profile, but now there is a mismatch?
I look at my MPC profile... middle name is there. Look at the partner profile... middle name is there. Call the partner... they confirm middle name is there and was transmitted to CX.
Try OLCI again, no joy.
Somehow, some button finally appeared to let me print the boarding pass "with errors", along with some no-fly warning. It printed with no middle name.
Flew no problem. When checking bags at ORD, they have no problem checking me in again.
Similar "mis-match" errors on the return flight. This time I was flying on an Asia Miles redemption! I booked it online, using my account. How can there be a mismatch?
I guess this just gets attributed to the notoriously poor Cathay IT staff.