Let me share one experience that was neither a battery problem nor a faulty iPhone. After my iPhone 6 (ios 10) got stolen, I've bought a brand new iPhone 6s (i

Let me share one experience that was neither a battery problem nor a faulty iPhone. After my iPhone 6 (ios 10) got stolen, I've bought a brand new iPhone 6s (ios 11) on the official apple store. It was totally unusable, all problems people shared I've had as well. It would take several seconds for an app to open, the phone would freeze for one minute, volume controls on the lock screen wouldn't work, my Bluetooth range was literally less than 10cm, sometimes when I called the phone would mute my voice. I've tried resetting the phone twice. No luck. Then I've downgraded to iOS 10 and all problems went away; performance was similar to my previous phone. So, no battery problem, no buggy phone, just a very very buggy operating system (or an OS that purposefully slows down on older devices).