Design of experiments (DOE) is a powerful tool for determining specific factors affecting defect levels in a product. When a medical devices company tested their upgraded surgical system used for life-saving operations, previously unknown system crashes occurred. Together with the client’s team of experts we applied DOE and identified the cause of the failure. Unexpectedly, it turned out that these crashes were due to an updated processing unit of a new batch of mainboards. While on paper the specifications of old and new mainboards were identical, replacing this unit solved the problem and the deadline could be met.