The full report is contained in a pdf on the linked page, but I have reproduced the IT-relevant sections below.
THE Root Cause of the it incident
The batch scheduler failure.
Banks generally update that day’s transactions in the evening. They use a software tool known as a batch scheduler to process those updates. A batch scheduler coordinates the order in which data underlying the updates is processed. The data includes information about customer withdrawals and deposits, interbank clearing, money market transactions, payroll processing, and requests to change standing orders and addresses. The processes underlying the updates are called “jobs”. Batch schedulers place the jobs into queues and ensure that each job is processed in the correct sequence. That day’s batch processing is complete when all balances are final.