I've been experiencing an issue that has causing me a lot of problems, as various apps including Whatsapp, Telegram, Linkedin, Authy, Lastpass, and more will randomly log out, and reset back to their inital state as if I just installed it on a clean phone. Apps like Whatsapp and Telegram will have lost all of their chat history, even if it was backup up on iCloud.
I've talked with Apple and they're adamant the problem is not with the hardware or with iOS after restoring the phone using iTunes. Whatsapp support is just giving me the run around with canned responses, so I doubt they know anything about the problem either.
I'm at a total loss as to what might be causing this problem after restoring the phone multiple times (the last time without restoring to a backup).
My phone is an iPhone 6S 64GB running iOS 9.3.2 although this problem has existed well before iOS 9.3.2 was released.
Best Answer
A found a 'satisfactory' workaround. As I commented on the question, I was having the bug after I decided to close all applications using the app switcher and then start every application on my phone.
My 'solution' is to close all applications in the app switcher and then turn off the device. Then, turn on the phone.
Since that, I have not had problems.