While Apple is expected to launch two bigger iPhone models this year, including a 4.7-inch iPhone 6 model and a 5.5-inch iPhone 6 (or iPhone Air) phablet, a new research note obtained by MacRumors from well-connected Apple insider and KGI Securities analyst Ming Chi Kuo says that the latter model might hit stores next year.

FROM EARLIER: New report claims to reveal release date for iPhone 6 and ‘iPhone Air’

This isn’t the first time reports have claimed the 5.5-inch iPhone 6 will be delayed, compared to 4.7-inch iPhone 6 launch plans, as Apple is facing production issues. While previous reports said that sapphire glass mass production will lead to 5.5-inch iPhone 6 delays, Kuo now describes new iPhone 6 manufacturing challenges.

“Production bottlenecks on 4.7-inch iPhone 6 center on the yield rate of in-cell touch panel and metal casing,” Kuo said. “As in-cell touch panel becomes larger in size, the edge of the panel may become insensitive to touch. Meanwhile, under new manufacturing process for the iPhone 6 metal casing, color unevenness is an issue.”

These problems seem to affect the 5.5-inch model even more than the smaller iPhone 6, which is why Kuo says Apple will either launch the 5.5-inch iPhone 6 in limited quantities after October, or launch only the 4.7-inch version and cut the prices of the iPhone 5s and iPhone 5c, which should continue selling alongside the new 4.7-inch version.

Apple is expected to announce its 2014 iPhone or iPhones in September, and start selling at least one model later that month.