When you create an Auto Task, you choose when the task should begin ("Schedule for") and you can also set a time frame for the completion of the task ("Can start from" and "Must finish before").
These task times are based on the scheduling of the relevant reservation. If, for example, the check-out time of a reservation changes, tasks with a "Confirmed" status for that reservation that are scheduled around Check out or have a time frame based on Check out will revert to "Pending". This is to help make sure the assignee of the task is aware of the change in schedule.
The tasks will be re-confirmed when the assignee accepts the task via the Guesty mobile app.