Issues with Audio added to slide or caption on a slide lossing last three words

I have uploaded a project to LMS and with Audio added to slides (some are video demos) and also captions and it is all working correctly.

I then uploaded a second project. This one the audio seems to stop before the last three words are heard. This can be for a single sentence or a paragraph and regardless of being added to a slide or a caption on a slide some of the slides are video demos. For example the sentence  'Clicking on to the link will enable you to access the form' you will only hear clicking on to the link will enable you to'

What is more confusing the second project the slides are the same slides as in project one. (I just saved the project with a different name and then added more slides at the end for a group of different users). I can't figure out why when the second project is uploaded the audio on the same slides no longer has the last three words.

I have tried republishing and uploading but it has made no difference.

Any help gratefully received as this is all new to me.