Traveled on several DONExs and never had a problem until this latest one when CX issued the ticket. I have had nothing but problems ever since. Trying to change, once changes have supposedly been made other airlines not being able to find the ticket number in the reservation etc etc. I think this post on the OneWorld site indicates that there are problems:
"By the time it joins oneworld, Mexicana will have completed the migration of its main IT platforms to Amadeus Altea - alongside oneworld partners British Airways, Finnair, Iberia, LAN, Malév Hungarian Airlines and Qantas, with Cathay Pacific also committed to transfer to this provider soon."