The one root-cause tool that gets skipped, and it's the reason your fixes don't stick
Spent 30+ years on plant floors watching teams "fix" the same downtime issue three, four, five times a year.
The pattern is always the same: something breaks, someone patches it fast, everyone moves on, and 6 weeks later it breaks again in a slightly different way.
The step that gets skipped almost every time isn't the 5-Whys — everyone does that one, even if half-heartedly. It's verifying the fix against the actual failure mode before closing the ticket. Teams write down a root cause, apply a countermeasure that sounds reasonable, and close it out without ever confirming the countermeasure actually addresses the mechanism that caused the failure. That gap is where "fixed" problems come back from.
A quick way to check yourself: after any RCA, ask "if I reversed this fix, would the original failure reappear exactly as it happened?" If you can't answer that with evidence (not intuition), you haven't verified the fix — you've just made a change and hoped.
This is the single highest-leverage habit I coach on, because it's cheap to do and almost nobody does it consistently under time pressure.
If you're deep in CI/Lean/Six Sigma work and want ready-to-use RCA frameworks and daily control systems built from real operational experience (not theory), I put together a set of playbooks and toolkits at OpexCoach — link in my profile. Happy to also just talk shop here if you're working through a specific problem.