Explanation
According to the PMBOK Guide, a project manager should engage stakeholders throughout the project life cycle and ensure their expectations and needs are considered and addressed. A critical stakeholder who was not consulted at the time of the schedule discussion may have valuable information, insights, or constraints that could affect the project schedule. The project manager should organize a new schedule framing meeting with the critical stakeholder to obtain input, clarify requirements, resolve conflicts, and reach agreement on the project schedule. This can help avoid rework, delays, and dissatisfaction in the future. Reaching out to the project sponsor, analyzing the root cause, or creating a new project schedule are not the best options, as they do not involve the critical stakeholder and may not address the underlying issue. References: PMBOK Guide,
7th edition, page 32-33, 36-37, 40-41.