Apple's much-awaited iPhone 5 may reportedly face some shipment constraints, courtesy a possible defect in the displays manufactured by one of Apple's touchscreen supplier Wintek. According to a report in DigiTimes, Taiwan-based Wintek has discovered a "delayed bubble" defect during the production of some iPhone 5 touch panels that may hit schedule. Wintek has since said that all its products are on schedule, and it is confident of meeting its shipping deadline. However, analysts believe that while the glitch probably won't cause a delay in launch of iPhone 5, it may cause some temporary supply shortages. According to DigiTimes, Wintek will provide 20 per cent to 25 per cent of all iPhone 5 touch panels, while Taiwan's TPK Holding will produce 60 per cent to 65 per cent of the device's displays. The report claims that Apple is expected to ship 25-26 million units of iPhone 5 in the fourth quarter.