Sounds like an OS issue.
This is my knock on Apple. Madness to think people are going to pay $695 every 18 months, forever.
Arrogance exemplified by the sealed battery case. The phones rot along the same sort of timeline as a well preserved Fuji apple in a refrigerator.
That’s actually true. My iPad Air from November 2013 is still very usable in 2016 running iOS 9.3.2 (thanks to 1 GB of RAM); however, I will likely finally replace it about 16 months from now because its functionality will be way behind the latest iPad models.