Open Radar

 
Area:
Something not on this list

Summary:
This is a problem that has spanned across multiple iOS devices and multiple iOS versions, and always appears to affect the same apps.

It appears that the UserDefaults for various apps is reset at random. I've noticed that third party apps like WhatsApp, Instagram, Authy, Telegram, LastPass and possibly more will "reset" back to their original state as if I just downloaded them for the first time.

I've also noticed this issue happens with my own iOS apps, where the only data I store is in the user defaults and it abruptly is lost.

Steps to Reproduce:
I will use the Instagram app as an example, as it is the most prone to being reset, however the process is similar for all of the affected apps:

1. Install the Instagram app
2. Log in
3. Suspend the app
4. Wait a few hours (sometimes takes overnight)
5. Resume the app

Expected Results:
The app to continue to function normally

Actual Results:
The app is "reset" back to its original state, requires me to log in again. All of the settings I have set are lost.

Version:
iOS 10.2.1 (14D27). Issue first noticed back on iOS 9.

Notes:
While this issue appears to only affect third party apps, it's clear that the issue is related to the UserDefaults API or how the phone stores these settings on disk. I've had difficulty troubleshooting this issue.

Configuration:
iPhone 6S 64GB.