Thanks for the reply Paul. We are still investigating it (we have the same problem as the initial poster). We think it can be caused of videos which is not correctly bitrate aligned. We will continue to investigate and post when we have more info/data to share.
Using JW player's MPEG-DASH player I don't see any issue with playback either. In fact I think it handles this particular stream better than our MPEG-DASH Test Player because after playing the content using the JW player I do see the content is longer than what is being played in the MPEG-DASH Test Player. For some reason I was only getting 21 seconds using our player.
I recommend that you test using the bigbuckbunny content and bigbuckbunny.smil file which can all be downloaded from the article below.