Production yield verification for a complex device, such as the flash memory, is a problem of primary importance due to high design density and current testing capabilities of such design. In this paper, the flow byte issue in the one time programmable block is investigated through physical failure analysis (PFA). The customer reported fail for this unit was flow byte error with flipped data loss in one of the bit. Various experiments were done on numerous units to identify the yield related issue and prevent shipment of such units to customers. The case study from this paper is beneficial to the FA community by showing the exact methodology in identifying the problem, its containment, and implementation of corrective actions on the ATE to prevent shipment of low yield units to customer. The yield was enhanced by implementing the containment and corrective actions on the ATE.