Apple has acknowledged display problems affecting some its first foldable iPhones, days after the device went on sale, and said customers experiencing the issue would be offered replacements. “We are aware of an issue impacting the inner display on a small number of iPhone Duo units,” the US technology company said in a statement, without disclosing what was causing the issue. “If users experience issues with their iPhone Duo display, they should contact AppleCare for a replacement."