Music stops during movie in Keynote

I've inserted music into the presentation and the song is 5 mins long. There are 21 slides. After exporting the presentation to a movie, and then playing the movie, the song stops playing at 41 seconds, at about the 4th slide. It doesn't matter if I move the slides arounds - the music always stops at 41 secs when saved as a movie.

When I am in Keynote the song continues throughout if I play the presentation from the start. I want the music to play in the movie through all the slides.

The music file is 5 mins long. It is set to play continuously per slide.