This summary is not the rule. The rule text controls.
Not every mistake made during a trial is enough to undo the result. If a judge makes a small error, like letting in a piece of evidence that maybe should have been excluded, that mistake alone won't automatically get the verdict thrown out or the case retried. The error has to actually harm someone's case in a real way before a court will step in and fix it.
This rule tells judges to look past small, harmless mistakes and focus on whether a party's basic rights were truly affected. The idea is that trials don't have to be perfect to be fair. If an error didn't change the outcome or hurt someone's ability to make their case, courts will let the result stand rather than starting the whole process over.
In practice, this means if you're appealing a case or asking a court to overturn a decision, pointing out that the judge made some kind of error isn't enough on its own. You have to show that the error actually mattered, meaning it likely affected the outcome or unfairly hurt your ability to present your side of the story.