Apple said it will replace iPhone Duo handsets that developed inner display problems within days of the device's launch last week.
Photos posted on social media show lines appearing across screens and cracks along the central crease of the foldable phone, which costs £1,999 ($2,668) in the UK. Some owners also reported a crunching noise when opening the device.
Apple said it is aware of "an issue impacting the inner display on a small number" of phones and urged affected users to contact the company for replacement. The company did not specify how many devices were affected. Some images of faulty phones may have been created using artificial intelligence, the BBC noted.
The Duo's 7.6-inch inner display connects via a central hinge. This complex engineering mirrors problems Samsung's Galaxy Fold experienced in 2019, when reviewers reported broken screens on early units.
One Duo owner, Justin Lokos, posted an image showing lines across the right side of his display, then shared a photo of a replacement handset he received from an Apple store in New York.
The Duo represents Apple's first major iPhone redesign in nearly two decades. When closed, it resembles a wide iPhone. When opened, it unfolds to a device similar to a small tablet computer. The phone costs up to £3,199 for its most expensive model.
Apple chief executive John Ternus, who took over from Tim Cook in September, unveiled the device last month. Ternus told an audience at Apple's California headquarters that the Duo would "redefine the experience of using a foldable phone," distinguishing it from competing foldables he described as "two phones awkwardly stuck together." The launch attracted crowds at Apple stores worldwide.