Apple Inc. (NASDAQ:AAPL) will reportedly launch its iPhone 6 in two screen sizes: 4.7-inch and 5.5-inch. Both versions were previously expected to be unveiled in September. However, KGI Securities analyst Ming Chi-Kuo said in a research note that the 5.5-inch model is facing several production issues, which could push its release to 2015. Kuo has a solid track record when it comes to Apple’s future product lineup.

iPhone 6 Phablet

iPhone 6 manufacturing issues

Meanwhile, the analyst said the 4.7-inch model is still expected to debut this fall. Inside sources told Kuo that Apple is facing production issues with the new in-cell touch panel technology and color unevenness on the redesigned metal casing on both models. But those problems are worse for the bigger model. Its larger size makes these issues even more complicated. In the 5.5-inch iPhone 6, there could be issues related to touch sensitivity on the edges of the in-cell touch panels.

Both versions of the iPhone 6 will reportedly sport in-cell touch panel technology, which allows for thinner construction. Moreover, Kuo believes the scratch-proof 5.5-inch sapphire display is unlikely to “pass the drop test near term.” It could also prompt delays. In the “most conservative scenario,” Apple could push the 5.5-inch iPhone 6 launch to 2015. In that case, the 4.7-inch version, along with the iPhone 5S and 5C, will drive Apple’s sales growth during the holiday quarter. That means the delayed launch of the phablet won’t have much impact on Apple’s bottom line.

Phablet iPhone 6 facing problems from all corners

In case the company manages to launch it in 2014, the device is unlikely to hit the shelves until mid-November, says Kuo. It’s not the first time the reports of the phablet iPhone 6 facing technical issues have surfaced. In the past, there were reports of display and battery life issues. But Bloomberg claimed last month that Apple has resolved those issues and both models will be launched at the same time.

Both versions of the upcoming iPhone 6 are expected to have a thinner design, an upgraded A8 processor, iOS 8, and improved cameras. Last week, Kuo said in another research report that Apple’s wearable device iWatch is also facing production delays.

Apple shares gained 1.62% to $96.76 at 12:06 PM EDT on Monday.