This summary is not the rule. The rule text controls.
Normally, if you want to challenge a mistake made during a trial, you have to speak up about it at the time it happens. If you don't object right away, courts usually won't let you raise that issue later, whether you're asking for a new trial or appealing the case.
This rule creates an exception to that requirement. If a mistake was so obvious and so damaging that it caused a real injustice, a court can still fix it, even if nobody objected at the proper time. The key word here is "palpable," meaning the error has to be clear and serious, not just a minor slip-up.
This gives courts some flexibility to correct major unfairness in a case, even when the normal rules for raising objections weren't followed. But it's not an easy standard to meet. The person asking for relief has to show that the error genuinely harmed their rights and that letting the result stand would be truly unjust, not just unfavorable to them.