Adobe Presenter playback issues on an IPad

We have published many presentations using Adobe Presenter 10 and Powerpoint 2013.  All all published with the following settings: 

Publish format - both SWF and Html5

Playback - auto play on start

Publish Audio - near CD Quality

Image Quality - medium

Control Preloading - disable preloading of embedded flash content

Certain presentations (but not all), when viewed from an IPad, are missing the "Play" button.  When it appears, it is in the center of the screen (center of the presentation slide), but in others, the "Play" button is not visible.  However, if you touch or click in the spot where the "Play" button should be -- it will play.  What would make the playback on some presentations to not show the Play button?  To the viewer, it appears that the presentation has frozen?

Secondly, and this seems only to happen on an IPad, some the slides cut off the audio before moving on to the next slide.  Our students are quite frustrated.  Does anyone know how to fix this?

Thank you.