Changing image type in the options should update that image, no need to alter the XAML
Steam can be a bit annoying in that regard. What I would assume is happening is that you launch the game and it brings up Steams stupid "loading popup" and then in the time between when it closes and the actual game is launched Big Box is regaining focus and playing the video again, and then the game loads after and Big Box doesn't recognize that fact and doesn't stop the video. We've had similar issues in the past. I'll take a look and see if there is a solid work around while we look at correcting that potential issue.