URL: http://www.dtmts.com/

Browser / Version: Firefox 57.0
Operating System: Windows 10
Tested Another Browser: Yes

Problem type: Video or audio doesn't play
Description: Video plays fine in Edge (with uBlockOrigin) but does not play in Firefox Dev Edition (v57 with uBlockO).
Steps to Reproduce:

1. Go to http://www.dtmts.com/
2. Click on Game to open player.
3. Video starts playing on Edge. Not so on Firefox. Firefox just shows a black screen with no player controls and does not load video.
   

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