A late failure means a transaction was successful and the money moved but later failed. This happens because banks and banking clients have a window of time where they can revert transactions or correct the completed status.
Most failures happen within three business days. However, it is possible that certain timeframes extend beyond this.
When a late failure occurs, you will notice the money move to its destination but come back days later. To understand why this happens review the transaction history to understand the source of the failure and take corrective action.
You can find a list of all failures and a brief description here.