Root cause analysis is a structured investigation that finds the underlying cause of a problem — the cause that, if removed, prevents recurrence. Symptom treatment removes the effect temporarily; root-cause treatment removes the problem permanently.
The toolbox: 5 Whys for depth, the fishbone diagram for breadth, data stratification to narrow down (when, where, which variants?). Verification is mandatory: a suspected root cause must be able to turn the problem on and off, otherwise it is only a hypothesis.
The sign of a weak analysis culture is recurring problems: the same stops, the same complaint types, the same fire drills every month. Time spent on root causes is the best-returning time in operations.