I'm sometimes having this problem when using video roSGNode to play streams: failed to create media player.
So I use a single video tag in the entire app, and just change the content data when play another song. The UI pages are switched inside another roSGNode, here are the children defined in my app scene:
<Video id="player" visible="false"/>
Sometimes even when I get this error, the playback can still working. Not sure if this is a memory problem, as when I quit app by "home" button, there are many orphaned objects. Reboot the device can solve the problem. Anyone knows the reason or solutions?