Why do i get error that level is not in build settings when i can see that it is in multiple ways?

Specifically I get the error message:> `Level '' (1) couldn't be loaded because it has not been added to the build settings. To add a level to the build settings use the menu File->Build Settings...` This appears in the debug output in Xcode /only/ for the iOS build of our game. Every other platform build does not have this problem and successfully loads the level. I can see the text data in ProjectSettings.asset is correct and the 'Build settings' UI also has a level number 1 which is the correct level. Aside from the error not occurring on other platforms the content of the scene in question are loaded and used correctly on these platforms. I have cleaned out the library and temporary files to the best of my ability... does anyone have any suggestions as to what I might have configured wrongly to achieve this? There is no indication of a problem during the build process - only when running on a device. Annoyingly - as an aside - the builds work okay in other respects, minus the functonality included in that scene, except on the original iPad mini which hard crashes about the time I expect to see this error in a debug build. This smells of a bug - at the least because everything works correctly on all other platforms I can test on. The contents of ProjectSettings.asset should be respected regardless as to any temporary data, caches or bad defaults... EDIT: I have now tested this on a clean machine and am able to reproduce the problem. I am raising a bug for this - in the meantime I will try using the string form of the function as workaround. EDIT: I have now tried the string version of the function and instead I get this 'complimentary' error message - but it also works correctly on all other platforms: > `Level 'bg_music_additive' (-1) couldn't be loaded because it has not been added to the build settings. To add a level to the build settings use the menu File->Build Settings...` EDIT: A crucial omission in the original question is that I am using LoadLevelAdditiveAsync. It turns out that LoadLevelAdditive works fine - if not asynchronously. EDIT: Bug raised - Case 597310. I have suggested a simple mitigation of making the error message accurate - something like: "LoadLevelAdditiveAsync does not work correctly for iOS - use LoadLevelAdditive instead" so this becomes trivial to identify and workaround until a real fix is provided (if ever).