I have an custom UIVIewController that is the base class for other controllers and has an instance of a custom UIView variable that is accessed by inherited the classes.
If anyone is having this issue after upgrading their tools and devices to iOS10, I had it and found that declaring them as weak, nonatomic in the .h file was the issue. I had never encountered this when doing so before but after removing (weak, nonatomic) from the property declaration, everything worked fine again.