Multiple instances of QMediaPlayer/QGraphicsVideoItem in same app

I am creating an app that shows multiple video using "videographicsitem" example as base for video element.
Many time starting the same app (that runs two videos) result in assert m_surface exception and when it starts (video run every time in loop: I have tried using playlist and manually restart video for each one) video in a surface disappear or after first restart video of first widget runs on the other widget and same for the latter one.
Video widget are indipendent from each other and are reentrant (QGrapicsVideoItem/scene/view and file name of video).
This just works in this manner under win8 64bit using Qt ANGLE 32bit; under win7
it always crash loading media.