The cameras of the iPhone 12 are software-protected against unauthorized exchange.
The problem was first discovered by Youtuber Hugh Jeffreys. The professional hobbyists from iFixit then verified it. The locking seems to be active only on the iPhone 12; the more expensive iPhone 12 Pro does not have the restrictions. It could also indicate that there are several incompatible cameras from different manufacturers on the iPhone 12, and both Jeffreys and iFixit randomly selected the cameras for repair. There were similar problems with the iPhone 7 and 8, reports The Verge.
The iFixit team also points out internal instructions from Apple that have leaked to them. There it is pointed out that after a camera or display has been repaired, the in-house system configuration app is required to teach-in the devices. Apple already uses the tool when changing the battery. Apple does not allow the exchange of Touch ID and Face ID components either - for security reasons, the company says.