According to the PMBOK Guide, a root cause analysis is a technique that involves identifying the underlying causes of problems or issues in a project. A root cause analysis can help the project manager and the team to understand the factors that contribute to the negative group behaviors and the lack of motivation and productivity. By conducting a root cause analysis session, the project manager can facilitate a collaborative problem-solving process that involves asking why the problem occurred, finding the root causes, and developing corrective actions to address them. A root cause analysis can also help to improve the team's communication, trust, and morale, as well as the project's quality, risk, and stakeholder management.
Defining and analyzing performance metrics, escalating poor performance to functional managers, or updating the stakeholder engagement plan are not effective actions for improving the project team's performance, as they do not address the root causes of the problem, and may create more resentment, frustration, or conflict among the team members. References: PMBOK Guide, Sixth Edition, pages 176, 558; PMI-PBA Guide, First Edition, pages 87, 102.