Apple has been busy of late, sending instruction manuals to its service centers about how to deal with the various bugs and issues being experienced by its customers with regards to some of its recent smartphones. Just a day earlier, the company was reported to have sent out instructions to its authorized service centers about how to resolve issues about a bug that disables the microphone on some iPhone 7 and iPhone 7 Plus units.

And now, a new support document sent to retail stores and Authorized Service Providers over the weekend explains best practices for resolving issues related to Face ID. According to a document obtained by 9to5Mac, Apple says that its technicians should first run a diagnostics test to see if Face ID issues can be resolved by repairing the phone’s rear camera.

Strange as it may sound, the front and rear cameras in an iPhone X are apparently interconnected, so problems with the phone’s rear camera may wreak havoc with Face ID, which is otherwise controlled by the phone’s TrueDepth front camera. Either way, the document goes on to say that if the diagnostics show that repairing the rear-cam won’t get the job done, the entire unit should be replaced, and the customer should get a new phone.

As 9to5Mac points out, iPhone X users have complained for a while that malfunctioning rear cameras are creating issues with Face ID, including Redditor Razerx1, who took to the message board just weeks after the iPhone X launch to narrate how a Genius Bar technician had told him as much even back then.