The Part That Failed
In my Caterpillar Dealer days I spent a lot of time on failure analysis. One I remember was a connecting rod sticking out the side of the block. The cause turned out to be excess gasket maker that clogged an oil passage. We had to answer a lot of questions before we got there.
What I learned is that the part that failed was usually not the cause. You started with the damage and kept asking what happened right before it. Each answer led you one step further back. Almost every time, the trail ended at something small and early, like a step in assembly that nobody was checking.
Leadership teams have the same problem. When an issue keeps coming back, keep asking why until you find the step nobody owns. Then assign it to one person.
