We are not aware of such an issue. Could you try to set the RadMediaPlayer.MediaElement.Source property to null?
If this doesn't help, you could try to replace the media player with MediaElement and check if the issue persists. RadMediaPlayer is using MediaElement internally which means the overhead can be caused by the MediaElement.
If suggested scenarios don't help, could you send us a sample repro project in order to investigate the root cause?
the Telerik team
Explore the entire Telerik portfolio by downloading the Ultimate Collection trial package. Get it now >>