In the software world, we have a common problem with changing requirements.
For example, as a customer (Product owner/Subject Matter expert), I state a requirement to develop a customer feedback feature. After I reviewed the feature, I changed my mind and asked to create a complaints module and remove the feedback feature.
It is common to have changing requirements within a software project. Such requests can be frustrating and require additional time and resources. We should avoid getting into such situations by empowering the Project team to ask good questions, validate and challenge requirements, and share experiences from other implementations.
However, within reason, changing requirements is not a bad thing either. Changing requirements may mean improving our understanding of the solution. The requirements may not have changed. Instead, our understanding of the solution may have improved.
So, as a Sponsor, consider handling change in requirements pragmatically. Developing a solution is an evolution. Therefore, we must be patient and support the evolution, knowing there will be changes along the way!