According to the Agile Practice Guide, one of the principles of agile project management is to "reflect on how to become more effective, then tune and adjust behavior accordingly" (Section 2.1). This implies that the project manager should facilitate regular retrospectives, where the team can inspect their work processes, identify what went well and what can be improved, and plan actions for the next iteration. By conducting a focused retrospective, the project manager can help the team to discover the root cause of why they had to work extra hours, and find ways to avoid or mitigate it in the future. This is also consistent with the PMBOKGuide, which states that "the project manager should use retrospectives to review the effectiveness of the project team and the project management approach" (Section 4.6.3.3). References:
* Agile Practice Guide, Section 2.1
* PMBOKGuide, 6th Edition, Section 4.6.3.3