My testing code: Start a video playing, and then run this method:

public async void OddballTest()

{

logger.Trace("OddballTest(): About to Pause");

MediaElement.Pause();

DELAY_OF_SOME_SORT_1

TimeSpan startingPosition = MediaElement.Position;

for (int i = 1; i <= 5; i++)
{
    logger.Trace("OddballTest(): About to Position +=");
    MediaElement.Position = startingPosition + i * TimeSpan.FromSeconds(10);
    DELAY_OF_SOME_SORT_2
}
logger.Trace("OddballTest(): About to Play");
MediaElement.Play();
logger.Trace("OddballTest(): Done");
}

• DELAY_OF_SOME_SORT_1 = nothing, DELAY_OF_SOME_SORT_2 = nothing: Playback freezes up, always. Usually there's MediaFailed events, sometimes not. e.ErrorException is always null.
• DELAY_OF_SOME_SORT_1 = await Task.Delay(10000), DELAY_OF_SOME_SORT_2 = nothing: Usually MediaFailed events, sometimes not. Sometimes the call to Play() succeeds and resumes video playback, sometimes it takes a couple calls to Play/Pause/Play/Pause/Play.
• DELAY_OF_SOME_SORT_1 = await Task.Delay(3000), DELAY_OF_SOME_SORT_2 = await Task.Delay(3000): Works perfectly. Able to see the intermediate frames as it steps forward in the video 5 times, and playback resumes properly.
• I tried a very short delay: ThreadSwitcher ResumeBackground followed immediately by ResumeForeground, which should be a single iteration of the main Render loop. Same behavior as no delay at all.
• I tried a slightly longer delay: await Task.Delay(20), slightly longer than 1 frame. Results were the same as no delay.