I talked to one of my friends at AA and the problem was with the trip trade (TT) system, not the monthly bidding system (PBS) like last year.

After the month's schedules are awarded, a TT system opens that allows pilots to pick up, drop, or trade trips. The system is not suppose to approve drops and trades which take the airline below minimum staffing levels for the affected days so, typically, drops on holidays would rarely be approved. The process is automated. The airline inputs the required staffing levels, the pilot's input their requests, then the computer crunches the numbers and makes the awards. Pilots will often put in requests that they know are unlikely to be approved because you never know when one will be approved unexpectedly. Something went wrong this month and it awarded all of the drops requested over Christmas.