According to the PMBOK Guide, a design change is a type of change request that modifies the product or service specifications, features, or functions. A design change might potentially add value to the project, but it might also affect the project scope, schedule, cost, quality, risk, and other aspects. Therefore, the project manager should not accommodate, consult, or convince the client without following the change management process. The change management process involves identifying, analyzing, documenting, presenting, deciding, communicating, and implementing the change request. The project manager should make transactional decisions focusing on the project goals, which means assessing the feasibility, desirability, and priority of the change request, and preparing a recommendation for the change control board (CCB). The CCB is the formal recognized group that reviews, evaluates, and takes decision on change requests. The CCB can approve, partially approve, or reject the change request based on the project goals, objectives, and constraints. The project manager should communicate the decision of the CCB to the client and implement the approved changes accordingly. References:
* PMBOK Guide's Change Management Process For PMP Exam
* Change Log - Project Management Knowledge
* Project Management Change Request Form & Process
* Change Log Template - Project Management Docs

When a key stakeholder expresses dissatisfaction with the deliverables, despite formal acceptance of the quality specifications, the project manager should review the requirements traceability matrix and conduct inspections. This allows for a detailed examination of whether the deliverables meet the agreed-upon quality standards and to identify any discrepancies. The requirements traceability matrix is a tool that links requirements throughout the project lifecycle, ensuring that they are addressed in the final deliverables. Conducting inspections is a method of quality control that helps to verify that the product meets the requirements and standards1.
References:
Discussions on PMP exam topics related to stakeholder dissatisfaction and quality control measures1.
PMI's A Guide to the Project Management Body of Knowledge (PMBOK Guide)2.
Professional in Business Analysis Reference Materials from PMI2.

The project manager should address the issue between the two team members by scheduling a meeting with them and using conflict resolution techniques to find a mutually acceptable solution. This way, the project manager can prevent the issue from escalating and affecting the project performance and team morale. This approach is consistent with the agile principle of fostering collaboration and trust among the team members12. References: 1: PMBOK Guide, 6th Edition, Chapter 9: Project Resource Management 2: Agile Practice Guide, Chapter 2: An Agile Mindset

According to the Project Management Professional (PMP) guidelines, learning from past experiences is a key aspect of project management. In this scenario, the project manager is aware of a similar project that was not successful. The best course of action is to review the lessons learned from that project and apply those insights to avoid repeating the same mistakes. This proactive approach can help improve the project's chances of success. References: PMBOK Guide, Project Management Knowledge Areas, Project Integration Management, Lessons Learned. Please refer to the specific sections in the PMBOK Guide and PMP study materials for more detailed information.

When a project budget is cut, it's important for the project manager to collaborate with the team to assess the impact of the change on the project1. This involves understanding how the budget cuts will affect different aspects of the project, including the scope, schedule, and quality. The project manager should then work with the team to develop an updated project plan that takes into account the reduced budget2. This approach aligns with the principles of servant leadership, which emphasize collaboration, team empowerment, and shared decision-making. References:
https://project-management.com/what-to-do-if-your-project-runs-over-budget-and-how-to-prevent-it/