If there is a gap in what stakeholders expect of a D&A project/initiative and what you had planned, what do you do? How do you determine if the expectations need to be adjusted or if the project itself needs to be re-worked to better meet those expectations?

Optimally, you would have fully understood the expectations at the onset of the initiative and ensured your deliverables align to then.  If this isnt the case and you'll fail to meet the expectations, then I would sit down with your stakeholders and break the news as quickly as possible.  If what you are delivering still provides some measurable benefits, I would try to negotiate with the stakeholder the keep the existing scope - and develop a plan to ensure your next project closes the gap between the current and future expectations. If your stakeholders see no value in what you're building, then I would revisit your requirements and timelines.  

Ultimately the decision will be based on expected ROI and outcome. Sometimes we can’t adjust expectations, for example compliance related projects. In that case, we need to rework the project to meet expectations