Since I add a localizable file to my project, I found this problem: the first time I load my app, I see the localised string of my key in a label, the second time I load the app, the key string in a label, the next time I load the app, everything is fine again.
the issue is that some vender plugins include a localizable.file again, and that my project include the same name file, so when I launch the app either of these two localizable string files were picked up.
So, u can rename your localizable file name, like MyString.string, and make it localization. use NSLocalizedStringFromTable to localize it.
NSLocalizedStringFromTable(@"Key", @"MyString", nil)