Weird temporary vertical stretch on iPhone5

One of the devices I use for debugging my app is an iPhone5. I have added the necessary loading screen for iPhone5 and the app looks just the way it should…

…except for this one time (at least this far) when all the images were slightly stretched vertically. I first noticed when the headers above some native textfields were partly covererd by the textfield (indicating that the native textfields were not affected). I closed the app and when I started it again the stretch was gone and everything looked normal again. I’m using an iPhone5 with iOS 8.1.2 and Corona SDK 2014.2511. I do not know if this is a Corona thing or an iPhone thing but I have never seen it before or since.

Has anyone experienced the same and if so, do you know what caused it?