You may remember that, back in July, Apple released rare bug-fix updates for older versions of its operating system: iOS 10.3.4 and iOS 9.3.6. This was necessary to help keep older iPhones and iPads maintain accurate location functionality as the GPS network goes through a time rollover transition.
However, the problem is even more serious for iPhone 5. Apple is sending out alerts to iPhone 5 owners that their phones must be updated to iOS 10.3.4 before November 3.