PMP Practice: Evaluate quality metrics and apply lessons learned

Birch Volkov is managing a medical device manufacturing project for Starfish & Ocean Petersen. The project follows a predictive approach with strict regulatory compliance requirements. During the manufacturing phase, the quality assurance team reports that 8% of the latest production batch failed initial inspection, slightly above the 5% threshold defined in the quality management plan. The manufacturing process has been stable for the past three batches, and this is the first increase in defect rates. The team has already documented the defects and isolated the affected units. What approach would be MOST effective for Birch to address this quality variance?