The unverified components were steel rods. SpaceX manufacture most of the complicated parts, but they buy nuts and bolts. Also, the steel rods were checked, but

The unverified components were steel rods. SpaceX manufacture most of the complicated parts, but they buy nuts and bolts. Also, the steel rods were checked, but only statistically, not each one. 1 in more than a thousand failed at 5 times lower than its design strength.