Publish a composition with a movie package containing an mp4 and an ogv.
Open in Firefox. The site loads fine.
On the desktop (outside of Edge Animate), remove the ogv movie from the media folder.
Open in Firefox. The preloader hangs, never handing off to the composition.
Return the ogv to the media folder.
Open in Firefox. The site loads fine.
Firefox should gracefully load the site even though it might not be able to play the ogv movie.
However, it appears that the composition is telling Firefox that a file is present when it is not.
Is there a workaround for this?