Get custom block type image field in Display Suite twig field
{% set image_uri = block_content.field_feature_row_image['#items'].entity.uri.value %}

&lt;img src=&quot;{{ image_uri|image_style('thumbnail') }}&quot;/&gt;

OR with a .0
{% set image_uri = block_content.field_feature_row_image.0['#items'].entity.uri.value %}

&lt;img src=&quot;{{ image_uri|image_style('thumbnail') }}&quot;/&gt;


If not, try
{{ file_url(block_content.field_career_highlight_image.entity.fileuri) }}


If still no dice, then give this a shot. In /sites/default/settings.php add:
// Override default twig method whitelist.
$settings['twig_sandbox_whitelisted_methods'] = [
  // Defaults:
  'id',
  'label',
  'bundle',
  'get',
  '__toString',
  'toString',
  // Additions:
  'url',
];

and then in your field twig put
{{ block_content.field_career_highlight_image.url }}