When work is repeatedly "nearly done" but fails iteration expectations and returns to the backlog, the most common control problem is weak adherence to the Definition of Done. The DoD is a shared, explicit quality and completeness standard that ensures increments are potentially shippable and reduces rework.
Emphasizing and reinforcing the DoD (C) addresses the systemic cause: inconsistent quality gates, missing testing, incomplete documentation, or unclear completion criteria. Updating acceptance criteria (B) can help at the user-story level, but acceptance criteria alone do not ensure the team's internal quality activities are completed (e.g., code review, unit tests, integration, security checks). Deferring fixes to the next release (A) normalizes technical debt and undermines predictability and value delivery. Extending iterations (D) masks the issue and harms cadence; it reduces transparency and does not improve quality discipline. Strengthening DoD usage improves throughput, transparency, and predictability-key agile objectives-and aligns with continuous improvement and quality management practices expected in PMP-aligned delivery.