According to the PMBOK Guide, 7th edition, section 4.3.2.1, when a project faces a technical issue that requires specialized knowledge or expertise, the project manager should consult with external subject matter experts (SMEs) and the team to find a solution. External SMEs are individuals or groups who have specialized knowledge or skills related to a specific aspect of the project, such as aerospace design. They can provide valuable insights, recommendations, and guidance to the project team. The project team consists of the project manager and the project staff who are responsible for performing the project work. They have the most knowledge and experience about the project and its deliverables. The project manager should involve both the external SMEs and the team in the discussion of the technical issue, as they can contribute different perspectives and ideas to resolve the issue. The project manager should also communicate the issue and the proposed solution to the project sponsor and other relevant stakeholders, but they do not need to be part of the initial meeting.
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PMBOK Guide, 7th edition, section 4.3.2.1
PMP Exam Content Outline, Domain II: Process, Task 5