Some audio not transmitted cp6

Hi captivate developers.

Some audio does not transmit, others do. For example: A file consisting of 20 scenes, each with a computer generated speaker voice. Most audio is audible, but at five scenes the voices do not transmit. It is a bit perplexing, since the audio works in principle, but not each time. So far the solution has been to re-create the file, re-publish, in some cases cut the publish file in two, etc. At some point of this trial and error it works. But this can't be the solution, just to much work.

Any idea what could be the root of the problem?

Thank you and kind regards.