All very interesting I'm sure, but wholly irrelevant to the empirical experience of the song for millions of people worldwide. Mistakes? Not at all - you might try thinking of it as one of the more evident manifestations of The Folk Process, rather than as yet another excuse for tedious pronouncements on Folk Correctness. I am English - we have various non-English words in our language which I'm sure we don't pronounce correctly not because we are mistaken in doing so, rather according to the happy pragmatic principles of common usage.