Apple Watch preorders are already booked solid into June, and a new report claims to reveal why the release has been delayed for so many customers. According to popular Apple analyst Ming-Chi Kuo, the company is facing production issues for a couple of key components in the new smartwatch.

Specifically, the issue could be caused by the new haptic vibrator included in the Apple Watch, along with its high-resolution OLED display. Kuo notes that the new vibration module has to be smaller and more accurate than the one found in the iPhone, which could be slowing down production from its Hong Kong supplier. Meanwhile, LG is apparently struggling to manufacture flexible displays that meet Apple’s requirements for lifespan and color accuracy.

Kuo also offers up an estimate on the number of Apple Watch preorders, putting the number at roughly 2.3 million units, adding that the company should be able to fill those orders by the end of May. He also suggests that 85 percent of early orders were for the cheaper Apple Watch Sport, with the Apple Watch Edition making up just 1 percent of preorders.

The news lines up with an internal memo from Apple’s retail chief Angela Ahrendts published earlier Thursday, which revealed that Watch orders would remain online-only through May. If the company is able to ramp up production in time for the summer, we’ll probably see some stock show up in its physical stores, but until then Cupertino may be struggling just to keep up with demand.