Apple Inc. is reportedly facing engineering and technical issues with its first-ever foldable iPhone models, according to a report by Nikkei Asia. The phone maker is encountering obstacles with both software and hardware and needs to make necessary adjustments. The pilot tests of the foldable iPhone models did not go as expected and could likely affect Apple’s (AAPL) stock prospects.

The report, which cited sources, said that the engineering snags could lead to a potential delay in manufacturing through mass production. A failure at this stage could also affect product shipment, leading to a delayed release of the flagship model. Apple stock, which remains rangebound this month, could see prices heading south if the snags are not rectified.

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The sources who spoke on the condition of anonymity explained that iPhone foldable phones could be delayed for months. “Engineering development issues could delay the ‌first shipments of ⁠the foldable iPhones by months in a worst-case scenario,” read the ⁠Nikkei report. If the flagship phones face hurdles, Apple stock would be the hardest hit among the Magnificent Seven.

People familiar with the matter said that it could take a longer time to make adjustments and resolve the technical snags. Reuters contacted Apple for a comment, and the Tim Cook-led company did not respond to the request. Apple releases its new iPhone models every year in September, and a delay in launch risks AAPL’s stock value.

CEO Tim Cook Sells $16.5 Million Worth of Apple Stock

The development coincides with CEO Tim Cook offloading $16.5 million worth of Apple stock on April 2. He sold the shares when AAPL was trading at the $251.25 and $256 range. In total, Cook made way with 5,087 shares, pocketing $16.5 million. AAPL has declined nearly 5% since the start of January and is marginally trailing the S&P 500 index.