DoD is mandatory in Scrum and not DoR. The information needed for Product Backlog items is provided by the Product Owner. Nothing interrupts the Sprint flow; for example, we don't postpone the Sprint because the items aren't ready. In such cases, the "unready" items would still be chosen for the Sprint and refined during it. If the Product Backlog items are unclear, the Developers forecast which Product Backlog items are most likely to meet the goal and create a Sprint Backlog based on an initial design and plan. Start the Sprint with the Sprint Planning and continue to analyze, decompose, and create new functionality throughout the Sprint. The Scrum team can discuss why this happened at the end of the Sprint in the upcoming Sprint Retrospective and what changes will make it less likely to happen again.