In a situation where a team member has made disrespectful remarks about another team member, it is the project manager's responsibility to address the issue directly with the offending team member. This can be done by coordinating a video conference to discuss the issue, understand the reasons behind the behavior, and find a resolution. This approach aligns with the principles of conflict management in project management, where the project manager is expected to handle conflicts within the team directly and professionally1. It's important to note that disrespect in the workplace is toxic and can affect the entire team and organization2. Therefore, it's crucial for the project manager to address such issues promptly and effectively. References: 2
https://www.getcampfire.com/blog/dealing-with-disrespect

In project management, it is crucial to prioritize work items in a way that maximizes business value and aligns with strategic goals. The PMI-PBA emphasizes the importance of assessing and prioritizing requirements to deliver the highest business value. This involves considering various factors such as stakeholder needs, regulatory compliance, and technical complexity. By focusing on delivering high-value items incrementally, the project manager can ensure that the project delivers tangible benefits at regular intervals, thus maintaining stakeholder engagement and support throughout the project lifecycle. References:
= The approach of prioritizing high business value items incrementally is supported by PMI's foundational standards and practice guides, including "A Guide to the Project Management Body of Knowledge (PMBOK Guide)" and "Business Analysis for Practitioners: A Practice Guide" which provide guidance on requirement prioritization and value-driven delivery12.

The lessons learned database is a valuable resource for reviewing past projects, which can provide insights into the performance and reliability of potential vendors. It contains historical information that can help in making informed decisions about vendor selection by analyzing previous experiences, challenges, and successes related to similar procurements1234.
References:
PMBOK Guide - Seventh Edition5
The PMI Guide to Business Analysis6
Business Analysis for Practitioners: A Practice Guide7

According to the Professional in Business Analysis (PMI-PBA) Guide, a change request is a formal proposal to modify any document, deliverable, or baseline. A change request should be submitted when there is a need to change the approved scope, schedule, cost, quality, or any other aspect of the project. In this scenario, the project manager and the team have identified a potential design problem that requires a revision of the approved design. Therefore, the project manager should inform the client of the problem and follow the change request process to obtain the necessary approvals and update the project documents accordingly. This will ensure that the client is aware of the issue and its impact, and that the project is aligned with the client's expectations and requirements. Conducting a proof of concept, amending the design specifications, or passing them to the development team are actions that should be taken after the change request is approved, not before. References: (Professional in Business Analysis Reference Materials source and documents)
* Professional in Business Analysis (PMI-PBA) Guide, Chapter 6, Section 6.4.1.1
* A Guide to the Project Management Body of Knowledge (PMBOK Guide) - Seventh Edition, Chapter 8, Section 8.2.2.1