On some of them the audio doesn't play

I am having two problems. One in quizes and one when coming out of quizzes.

I am building a series of seven similar courses to be taken in series.
Each has an opening, the material, a summary, and a quiz, followed by, depending on whether they pass the quiz or not, a "pass" slide with an audio file attached that instructs them how to continue with the course, OR a "fail" slide that has no audio.

On most of the modules the sound on the "pass" slide plays fine, but on two the file does not play in the published file set. It DOES play when I PREVIEW the Presentation.

Anyone have any idea what is going on and how to fix it?