Manufacturers issue a when a defect is found after many models have been sold. manufacturers issue a when a defect is found after many models have been sold.

They issue recalls. A recall is when a company realizes that a product has a defect that might be dangerous or causes the product to malfunction. When a thing is recalled, all stores selling it send it back to the manufacturer, while people who bought it are allowed to return it for repair or often to get another product instead of that one for free. 

Using these strategies on tests will improve your own test taking skill because it may inform you of strategies you were unaware of before reviewing them.