The Touch ID sensor is one of the most notable features that sets the iPhone 5s apart from its predecessor, the iPhone 5, as well as its lower-priced sibling, the iPhone 5c. Users generally reported positive experiences with fingerprint recognition accuracy and speed, but problems began appearing after a few months of use.
The sensor, or the software behind it, seems to be "forgetting" fingerprints enrolled by some users. Going through the initial setup process again seems to take care of the problem, but it recurs again after a few months. The problems also appear to be unrelated to conventional fingerprint scanner problems such as changes in skin texture, moisture, or dirt on or under the sensor surface. Damage to the sensor itself is an unlikely culprit, since Apple has used a protective sapphire glass disc in its design.
Apple's own support forums have several threads created by people describing troubles with the sensor. While the company has not yet made an official statement on the matter, AppleInsider cites sources close to Apple who say that a software update will soon be released.
Apple is also reportedly gearing up to launch iOS 7.1, which might include the Touch ID fix. iOS 7.1 could be released as early as next week, when the recently announced CarPlay experience for iPhone-powered in-vehicle entertainment and navigation is rolled out.