In his recent book, Heath Adamson describes the process of correctly diagnosing a problem:

Horst Schulze, the former COO of Ritz-Carlton Hotels, told the story of one manager's discovery of a problem that seemed to confuse almost everyone. Numerous complaints came in to management because room service was repeatedly delayed. The eggs were cold, the toast was hard, and guests were inconvenienced. Mr. Schulze described a typical response as being something along the lines of scolding the supervisor for being incompetent. As one could expect, the discouraged supervisor would then gather their staff around and do the same to them. Blame would cascade down from one person to the next. But this isn't what happened at the Ritz-Carlton.

The Ritz-Carlton manager assembled the team, and they studied the problem. The kitchen staff prepared the food on time. The staff quickly took the trays to the elevator for delivery. They discovered that the issue had nothing to do with the kitchen staff but rather the service elevators were not always available. This delayed delivery. Then, they continued to study the situation by using a stopwatch to time the elevators for an entire morning.

The reason the food was delayed and arriving to the rooms cold had nothing to do with irresponsible kitchen staff or faulty elevators. A decision by management to reduce the number of bedsheets on each floor was causing the housekeepers to use the elevators more frequently, thus tying them up more. Trying to save money by reducing the number of bedsheets purchased, stored, and washed actually created more challenges in the long run and resulted in angry customers and poor room service. Misdiagnosing a problem never results in solving it.