iPhone 6s and 6s Plus owners have reported that their devices are switching off for no reason.
This happens even when the phone is unattended and has a charged battery.
MacRumors reports it is unknown what causes the smartphones to shut down, but some with the problem have reported their Home button feels warm when trying to unlock their phones.
While the majority of the reports come from 6s owners, some iPhone 6 owners have have also reported the issue.
This has led some to believe that a glitch in iOS 9 may be the cause of the problem.
According to the reports, to turn an affected phone back on requires a user to hold the power and home button for 10 seconds – forcing a restart.
The iPhone 6s and 6s Plus are set to go on sale in South Africa on 16 October.