Embedded Video: Fullscreen Button Not Working (HTML5)

I have a project where I'm embedding an event video on a slide and publishing the project to HTML5.

One of the big benefits I see to using HTML5 output is that it forces the browser to embed and provide the playback controls for the video, and that includes a fullscreen toggle button. However, I'm finding that often (not always, but usually) the fullscreen button does nothing when clicked.

Anyone seen this and found a workaround? 

Later today or tomorrow I'll try moving the video files to a media server and just stream via a web object. I'll report back if that fixes the problem. But wanted to check here in the meantime.