Why does iOS sometimes turn off animation?

Question

I'm not sure what causes it, but I and other members of my team found that for some reason, iOS sometimes decides to completely disable all animations in our application . General iOS animations (parallax, application switching, home button, etc.) are still included, so they are limited to our application.

This would not be a problem if it were not for the fact that some things like -[UIResponder becomeFirstResponder] do not work immediately after what would otherwise be a ghostly animation (for example, in viewDidAppear or block a -[UIViewController dismissViewControllerAnimated:completion:] ).

I checked our code to make sure that this is not what we are doing, and indeed we simply pass YES to the Cocoa Touch structure when it asks if we want to animate something, and in no case in our code (or as far as I know, in our third-party SDKs) it’s called +[UIView setAnimationsEnabled:] . Similarly, I did nothing in the iOS settings, such as “Reduce movement”, and just restart our application or let the sleeping iOS device cancel this state.

So, what could cause iOS to disable our application for using system animations? Also, does this affect how / when / if delegate methods and callback blocks are invoked?

Also, is there a way to detect, run, or cancel an iOS solution to turn off animation?