One of the “best practices” touted by some experts is to determine the failure cause during a repair. Often, this is reasonable and achievable. In many cases, however, it’s not. And even when it is, field techs might not have the time, expertise, or equipment to accurately determine the failure cause.
In one plant, repair techs rushed from one downtime incident to another, but had to check a box on a list of failure causes. This information was put into a spreadsheet for Pareto analysis so resources could be focused on the most important issues. The fly in this ointment was time-pressed techs often just guessed (and guessed wrong). Resources were misdirected until management figured this out.
You may have noticed that while police respond to a murder scene, it’s the medical examiner who determines the cause of death. This division of labor is not a bad approach for industrial maintenance.
For certain kinds of failure and/or equipment, assign a “medical examiner” to the case. For example, any time a 100-hp motor fails you send it to your motor shop along with evidence collected at the scene.