Update #1:
iOS 9.0.2 is released.
Update #2: Issue confirmed in isolated cases at
Apple forums
Update #3: New survey questions (thanks notgreg)
Update #4: A possible fix has arrived.
View the latest data here.
Issue:
Many users have found out that their iPhone 6S, 6S+ (some 6) turns off by itself, even when left unattended. It is fixed by forcing a restart of
holding the home and power button for 10 seconds. Had this issue? Read below.
Is this problem a priority bug fix for Apple?
I was told by an Apple rep that this error isn't well documented. Based on our survey, this is probably because it is not identifiable in diagnostics. There are not very many common links between any of our diagnostics reports.
What causes it?
I've been told that at least one of (many?) possible causes is likely corrupted iCloud backups. If you've restored your device from any previous backup through iCloud, and that backup is corrupted, it could result in this problem. There has been some acknowledgment that iCloud still has bugs.
How should I fix it?
1. Method 1: (for those who setup a device as new OR restored from backup)
Reset all your settings and test for a couple days for stability before attempting anything else. (Settings > General > Reset > Reset All Settings>
2. Method 2: (for those who restored from backup)
If #1 fails, make sure all your iCloud data is saved then setup as a new iPhone (
here). You'll need to re-download all your apps manually so create a list first. Your iCloud data can be synced from your account, so that part is covered.
The key is to get a clean install and then create a backup from there. Then, create a backup on iTunes (not iCloud) and save that one. Test for a few days and if it's okay, you can create an iCloud backup again.
Please report your results after trying these. Especially if the problem is still not fixed.
Setting up your device as new means you are responsible for your backups. Please ask Apple support if you aren't comfortable.
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Survey:
The survey is still open but the spreadsheet is paused for now. If you are a beta tester, submit it to Apple's bug report as well. The more they see, the higher priority it gets.
1. Model, OS, and actions before the problem occurred.
2. Was the device started as new, or restored from a backup?
3. Was it restored through iTunes or restored through iCloud?
4. Has the device logged any kernel panics?
5. Has the device displayed a heat warning prior to shutting down?
Kernel Panics:
Settings>Privacy>Diagnostics & Usage>Diagnostics & Usage Data.
-There is no need to scroll through the list, as the only important logs will be at the top and they will start with a long string of numbers. (
example here)
Sample Diagnostics:
1. iPhone 6S 64 GB Gold, iOS 9.01, idle state
2. Restored from backup
3. Restored through iCloud
4. None
5. None