There are a plethora of tools that go into a problem analysis, six sigma, lean, or whatever labelled toolbox.

The important thing is being able to use the tool, not just do it, as the parent mentions in their comment:

It's easy for a manager to say "do a 5 whys". It's another to be able to support fixing what it finds out. Or if not your manager and just you or a small team with seemingly everything in your control to introspect and challenge assumptions or prior work that might need rethinking. That's the hard part.