In the context of an agile project, it is essential to foster a collaborative environment where knowledge sharing and coaching are integral to the team's success. When a lack of knowledge in a specific framework is identified as the root cause for decreased productivity, the project manager should encourage team members to share their expertise and provide coaching to those who need it. This approach aligns with the principles of agile methodologies, which emphasize team collaboration, continuous learning, and adaptability. By promoting knowledge sharing and coaching, the project manager can address the knowledge gap directly and efficiently, without the need for external training or adding new team members, which could disrupt the team's dynamics and may not address the root cause effectively.
References: The answer is verified by the principles found within the PMBOKGuide's sections on Project Resource Management and Agile Practices, as well as the Professional in Business Analysis Reference Materials, which emphasize the importance of team development, knowledge transfer, and continuous improvement within project teams.