Apple has almost fixed a power-management issue that
Apple News Page 2CachedWith
iPhone 6S: Fixing Issue With Random Screen Turn Off / Shutdown (Power Lock Fault)
Apple says iOS 10.2.1 has reduced unexpected iPhone 6s shutdown issues by 80%
Apple's iOS 10.2.1 addresses unexpected iPhone 6, 6s shutdowns
The Most Common iPhone 6 and 6 Plus Problems, and How to Fix Them
Usual iPhone 6s Problems When/After Upgrading to iOS 14/13
How to Fix an iPhone 6s That Randomly Shutdown or turns off
iPhone Battery Shutdown Issue - What can you do?
iOS 10.2.1 Is Reducing Those Pesky Random Shutdowns for iPhone 6 and 6s Owners
How to stop your iPhone shutting down unexpectedly
Is Apple intentionally producing its products to last shorter? - Quora