Video Asset URLs not rendering
Asset fields return like an array so they can potentially have more than one item, you need to request the first item only with .one() (as opposed to requesting .all())
//First check if the asset field has more than zero items
{% if block.video.videoFileWebm|length %}
    // Retrieve the first and only item in the asset field
    &lt;source src=&quot;{{ block.video.videoFileWebm.one().url }}&quot; type=&quot;video/webm&quot;&gt;
{% endif %}

I would also set block.video to a variable to clean up the code a bit and maybe speed it up a little.