Story JSON doesn't produce valid video but amp works

[hackable]

This works well for amp but not for video generation

{
  "version": 1,
  "title": "Story Title",
  "canonicalUrl": "https://example.com/story",
  "preview": {
     "publisher": "Story Title",
     "publisherLogoSrc": "https://news.files.bbci.co.uk/include/vjassets/img/bbcnewsicon256x256.png",
     "posterPortraitSrc": "https://example.com/publisher-logo"
  },
  "meta": {
    "datePublished": "2018-05-21",
    "dateModified": "1527857615255",
    "author": "BBC",
    "authorType": "Organization",
    "images": [
      "poster-square.jpg",
      "poster-portrait.jpg",
      "poster-landscape.jpg"
    ],
    "publisher": {
      "name": "BBC",
      "logo": {
        "url": "/bbc-news.png",
        "width": 600,
        "height": 60
      }
    },
    "description": "Some story description"
  },
  "bookendConfigSrc": "bookend.json",
  "pages": [
    {
      "layers": [
        {
          "type": "container",
          "styles": {
            "background-color": "black"
          }
        },
        {
          "annotation": "a image element",
          "type": "image",
          "source": "https://c.files.bbci.co.uk/F081/production/_106196516_fishcover.jpg",
          "layout": "responsive",
          "width": "720",
          "height": "1080",
          "alt": "an image"
        },
        {
          "type": "container",
          "styles": {
            "flexDirection": "column",
            "justifyContent": "flex-start",
            "alignItems": "flex-start",
            "padding-left": "24px",
            "padding-top": "22px",
            "backgroundLinearGradient": {
              "direction": "180deg",
              "stops": [
                {
                  "color": "rgba(0, 0, 0, 0.5)",
                  "distance": "40px"
                },
                {
                  "color": "rgba(0, 0, 0, 0)",
                  "distance": "100px"
                }
              ]
            }
          },
          "elements": []
        },
        {
          "type": "container",
          "styles": {
            "flexDirection": "column",
            "justifyContent": "flex-start",
            "alignItems": "flex-start",
            "padding-left": "24px",
            "padding-top": "22px",
            "backgroundLinearGradient": {
              "direction": "0deg",
              "stops": [
                {
                  "color": "black",
                  "distance": 30
                },
                {
                  "color": "transparent",
                  "distance": "50%"
                },
                {
                  "color": "rgba(0,0,0,0)"
                }
              ]
            }
          },
          "elements": [
            {
              "type": "image",
              "source": "https://news.files.bbci.co.uk/include/newslabs/ampstories/en/clear_strip_logo_22.png",
              "width": "147",
              "height": "22",
              "alt": "BBC News logo"
            }
          ]
        },
        {
          "type": "container",
          "styles": {
            "flexDirection": "column",
            "justifyContent": "flex-end",
            "alignItems": "flex-start",
            "paddingLeft": "32px",
            "paddingRight": "32px",
            "padding": "25px"
          },
          "elements": [
            {
              "type": "paragraph",
              "text": "Some text",
              "styles": {
                "color": "#ffffff",
                "fontFamily": "sans-serif"
              }
            },
            {
              "type": "container",
              "styles": {
                "border-bottom": "4px solid #bb1919",
                "animate-in": "fade-in",
                "width": "200px",
                "padding-top": "10px"
              }
            }
          ]
        },
        {
          "type": "container",
          "styles": {
            "flexDirection": "column",
            "justifyContent": "flex-end",
            "alignItems": "flex-end",
            "padding-right": "0px"
          },
          "elements": [
            {
              "type": "paragraph",
              "text": "Credit TEST",
              "styles": {
                "color": "#ececec",
                "backgroundColor": "rgba(0,0,0,0.6)",
                "fontFamily": "sans-serif",
                "padding": "3px 8px 1px",
                "fontSize": 13
              }
            }
          ]
        }
      ]
    },
    {
      "layers": [
        {
          "type": "video",
          "loop": true,
          "layout": "responsive",
          "height": 1280,
          "width": 720,
          "sources": [{
            "source":"https://vod-pro-ww-live.bbcfmt.hs.llnwd.net/av_pv25_pa3/modav/bUnknown-c9c0bec1-5d17-4c16-9b0d-315e1b03a5a2_p0735wqz_cUnknown_1552304950246.mp4?s=1553931253&e=1553974453&h=7396b6b6ecf530fbf5e7bb8e6d57c1c8",
            "type":"video/mp4"
          }]
        },
        {
          "type": "container",
          "styles": {
            "flexDirection": "column",
            "justifyContent": "flex-start",
            "alignItems": "flex-start",
            "padding-left": "24px",
            "padding-top": "22px",
            "backgroundLinearGradient": {
              "direction": "180deg",
              "stops": [
                {
                  "color": "rgba(0, 0, 0, 0.5)",
                  "distance": "40px"
                },
                {
                  "color": "rgba(0, 0, 0, 0)",
                  "distance": "100px"
                }
              ]
            }
          },
          "elements": []
        },
        {
          "type": "container",
          "styles": {
            "flexDirection": "column",
            "justifyContent": "flex-start",
            "alignItems": "flex-start",
            "padding-left": "24px",
            "padding-top": "22px",
            "backgroundLinearGradient": {
              "direction": "0deg",
              "stops": [
                {
                  "color": "black",
                  "distance": 30
                },
                {
                  "color": "transparent",
                  "distance": "50%"
                },
                {
                  "color": "rgba(0,0,0,0)"
                }
              ]
            }
          },
          "elements": [
            {
              "type": "image",
              "source": "https://news.files.bbci.co.uk/include/newslabs/ampstories/en/clear_strip_logo_22.png",
              "width": "147",
              "height": "22",
              "alt": "BBC News logo"
            }
          ]
        },
        {
          "type": "container",
          "styles": {
            "flexDirection": "column",
            "justifyContent": "flex-end",
            "alignItems": "flex-start",
            "paddingLeft": "32px",
            "paddingRight": "32px",
            "padding": "25px"
          },
          "elements": [
            {
              "type": "paragraph",
              "text": "Some text",
              "styles": {
                "color": "#ffffff",
                "fontFamily": "sans-serif"
              }
            },
            {
              "type": "container",
              "styles": {
                "border-bottom": "4px solid #bb1919",
                "animate-in": "fade-in",
                "width": "200px",
                "padding-top": "10px"
              }
            }
          ]
        },
        {
          "type": "container",
          "styles": {
            "flexDirection": "column",
            "justifyContent": "flex-end",
            "alignItems": "flex-end",
            "padding-right": "0px"
          },
          "elements": [
            {
              "type": "paragraph",
              "text": "Credit TEST",
              "styles": {
                "color": "#ececec",
                "backgroundColor": "rgba(0,0,0,0.6)",
                "fontFamily": "sans-serif",
                "padding": "3px 8px 1px",
                "fontSize": 13
              }
            }
          ]
        }
      ]
    }

  ],
  "defaultStyles": {
    "heading": {
      "fontFamily": "sans-serif"
    }
  }
}