When your automated tests fail, how many failures are real? Anywhere from none to all of them.
False failure rates in test automation span the entire spectrum. Some test runs produce zero false positives. Others flag nothing but phantoms. You can't know which category you're in until someone manually investigates every red flag.
One team spent 23 hours triaging 300 test failures. Nearly three full workdays of an engineer checking whether each failure represented an actual defect or just a flaky test, a timing issue, a locator that drifted when someone updated the UI. As test suites grow from hundreds to thousands of cases, even modest false failure rates compound into days of weekly verification work.