depends on the type of error and whether civil or criminal.
e.g., no reason to give judgment to a one party merely because the other party got some extra evidence before the jury that they shouldn't have had. we allow a "do over" without the "bad" evidence.
also, e.g., no reason to give judgment if the appealing party lost a motion to dismiss based on jurisdiction. the remedy = remand because you're just saying "the court has jurisdiction to hear the rest of the case"; there was no "rest of the case" already, so things have to proceed in the trial court further.