Audio problem: At the end of the movie, Marilyn and Miles have their first "real" kiss. After their lips touch the first time we see a shot of Miles' profile. You can tell that his lips are moving like he's saying something, but no sound comes out of his mouth.
Audio problem: The producer sings along Simon and Garfunkel's "The boxer", but changes the lines "Just a come on from the w*ores on 7th. avenue" to "just a come on from those gals on 7th avenue". I'm sure the Coen Bros. did it deliberately. And strangely enough, when the song is played during the final credits it's the original text. (00:01:15 - 01:34:50)