It doesn't play at all on my tablet, the movie window just goes blank. On my PC (Win 10 64-bit home edition) the first time playing it gives the message:
Failed to execute 'appendBuffer' on 'SourceBuffer': This SourceBuffer is still processing an 'appendBuffer or 'remove' operation.
It plays immediately after I refresh the page but when I try to skip ahead in the play bar it just buffers forever. Hope that helps.