Fixed it! So our app was creating a RootViewController which was extending UIViewController Inside the RootViewController, we create a UITabBacontroller and add it's view as a sub view of the RootViewController Slightly odd I know, might have picked this up from an online post. This has been working fine with no issues for over 10 years The fix was to instead make the RootViewController extend UITabController (and therefore no longer needing to add to any sub views) The problem then went away Hope this help somebody else

The app is as you say, a simple tab bar controller with a number of tabs and on each tab, the screen allows the user to go to child screens using pushViewController, although in the screenshot I've not even got that far. Thanks for replying, as you say it looks like the next step is a test app and then submitting a fault to Apple Odd though, this app has been fine since ios5!