Android: MediaPlayer is unstable when streaming mp4 video

I tried to create a simple qml file to play a video from a URL.
It works when run on the desktop, but it fails most of the times when run on Android.
In Android, I noticed that works with small videos (i.e: http://techslides.com/demos/sample-videos/small.mp4), but fails with longer ones (i.e: http://download.qt-project.org/learning/videos/Qt5_Thiago_Macieira_on_Qt_Core.mp4). The long video works sometimes after a few attempts. Might it be related to some sort of timeout when the Wi-Fi connection is not good enough?

These lines are printed in the android Log when the video cannot be loaded:

D/MediaPlayer(29354): Couldn't open file on client side, trying server side
E/MediaPlayer(29354): Attempt to call getDuration without a valid mediaplayer
E/MediaPlayer(29354): error (-38, 0)
E/MediaPlayer(29354): Error (-38,0)

The first line is printed when it is starting to load the video, while the last 3 lines appear after 3-4 seconds. When it works the last 3 lines are not printed.