Apple probably suspected that the iPhone X’s Face ID would be a contentious feature. From the moment it appeared to (but apparently didn’t) fail during the onstage demo, people have argued over the safety and effectiveness of using facial recognition to unlock the phone. But this might not be the only problem with the system — it could also affect the availability of the iPhone X when it launches in November.

Both the Wall Street Journal and Japan’s Nikkei newspaper claim there have been issues with the production of the 3D sensors used by Face ID. The problem components have been dubbed Romeo and Juliet; the former is used to project the 30,000 dots onto a user’s face, while the latter refers to the infrared camera that reads the pattern.

Anonymous sources say the extra time it takes to manufacture the Romeo modules compared to the Juliet modules has created an “imbalance in supply.” The situation reportedly led to a bottleneck in production, which could see Apple struggle to meet iPhone X demands when the handset is released on November 3. One source said the phone was being produced in quantities of tens of thousands daily, rather than hundreds of thousands.

The situation could be part of the reason why Apple is launching its handset weeks after the iPhone 8. The WSJ also said that the failed attempts to embed Touch ID under the iPhone X’s screen may also have been a factor in its delayed release date.

After last week’s launch of the iPhone 8 saw disappointing turnouts, Apple will want to make sure its flagship device isn’t in short supply. If availability remains limited for an extended period, some potential buyers may turn their eye to rivals such as the Note 8 and Google’s upcoming Pixel 2.

For those intending to buy an iPhone X no matter how long they have to wait, remember: if being robbed, squeeze the sides of the handset when handing it over. This will disable Face ID and prevent thieves from unlocking the phone by forcing you to look at it.

In other Face ID news, Apple has published a security guide warning that children under 13 shouldn’t use the system due to the probability of a false match being much higher. The company says this is because young children's “distinct facial features may not have fully developed.” The company also advises people with twins who have security concerns to use a passcode instead of Face ID.