The best way to resolve any stakeholder issues is to communicate with them directly and openly. Setting up a meeting with the stakeholder will allow the project manager to understand their expectations, needs, and concerns, and to negotiate a mutually acceptable solution. Moving to a predictive approach, talking to the team separately, or scheduling a team retrospective will not address the root cause of the problem, which is the stakeholder's dissatisfaction with the product concept. Moreover, these options may create more confusion, conflict, or delay in the project. References:
* PMBOKGuide, 6th edition, page 518: "The project manager should proactively and regularly engage with stakeholders to understand their needs and expectations, address issues as they occur, manage conflicting interests, and foster appropriate stakeholder engagement in project decisions and activities."
* PMI-PBA Guide, 1st edition, page 35: "The business analyst should communicate with stakeholders to elicit, analyze, and validate their needs and expectations, and to facilitate collaboration and consensus-building."