I've had occasional video pausing on Windows due to the integration with the keyboard media controls: sound from another source pauses the video and it doesn't restart with the other sound ends. I don't know whether that is a possible issue on Linux, but you can take that out of the equation as follows: (1) In a new tab, type or paste '''about:config''' in the address bar and press Enter/Return. Click the button accepting the risk. (2) In the search box in the page, type or paste '''mediak''' and pause while the list is filtered (3) Double-click the '''media.hardwaremediakeys.enabled''' preference to switch the value from true to false Any difference?