Why does my Galaxy 5 Active video player stop during playback of videos?

[AC Question]

The video playback used to work fine but now it stops, I press the play button and the video plays for a few seconds and stops again. When the symptom started the video played for several seconds then stopped. When I pressed the 'play' arrow the video would restart and finish the video. Now the video plays for a few seconds, stops, I press play and the video runs for a few seconds and then stops again ... this is now happening many times during each video.