On February 16, 2017 a Ford employee reported to others within the Ford organization that the second row seatbelt anchor bolt had fractured in his 2015 Lincoln MKC. Subsequent analysis by the Ford Central Labs would determine that the failure was intergranular in nature and had initiated from a thread lap. They also discovered that the surface hardness was greater than the specification. As the investigation deepened and attention was drawn to the hardening process, Ford would learn that the heat treater of these parts had experienced a power outage resulting in an inadequate temper.
Although such occurrences are extremely rare, this example reminds us that manufacturing or manufacturing process defects are a real-world event that occasionally result in fastener failure.