Apple has issued a new repair policy for some iPhone X devices which suggests that issues affecting the rear camera could be behind Face ID failures.
According to an internal document seen by Apple news blog MacRumours, stores authorised to fix faulty iPhone X models could be able to resolve the issues by repairing the rear camera.
The fix has confused onlookers as the Face ID feature – which unlocks the phone by recognising the user's face – is operated from the front camera of the iPhone X.
If the rear-camera repair does not fix Face ID, the stores are now authorised to perform a whole unit replacement instead of a display repair.
The company did not immediately comment on the release of the internal guidelines.
Repair shops are encouraged to run the Apple Services Toolkit 2 (AST2) which is a diagnostic service available to certified Apple service providers.
The fix comes as shares in Apple rise following solid phone sales growth in the latest quarter, despite fears over demand for the iPhone X.
Wall Street was also cheered by the announcement of $100bn in share buybacks, doubling the reward for investors compared to the same period last year.
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The stock climbed 3.6% in after-hours trading after Apple reported best-ever second quarter revenues of $61.1bn (£44.9bn), up 16% and ahead of expectations.
Apple also reported sales of 52.2 million iPhones for the three months to the end of March, up from 51 million a year earlier – only just missing a Wall Street target of 52.3 million.