Mobile Checkout Address Form UX: The Validation Bug We Missed Before Launch

Problem I ran into A small ecommerce client asked why mobile checkout drop-off jumped after a shipping form redesign. The desktop flow was fine, and the Figma file looked clean on a 390px frame, so at first it sounded like a traffic-quality issue. But session replay told a different story. Users were typing a ZIP code, selecting a state, tapping Continue, then getting bounced back to the same…