migrate d7 to d8: Fatal error: Call to a member function getFileUri()

Trying to upgrade a D7 site to D8, fails at same stage every time. Initially tried with front end tool and now through Drush but same error. Any ideas how I can fix this. I have no idea unfortunately.

$ drush @gsc migrate-upgrade --legacy-db-url=mysql://root@127.0.0.1/my-d7-db --legacy-root=http://dev-local.my-d7-site.com
Upgrading contact_category
Upgrading d7_dblog_settings
Upgrading d7_filter_format
Missing filter plugin: filter_null. [error]
Missing filter plugin: filter_null. [error]
Upgrading d7_filter_settings
Upgrading d7_global_theme_settings
Upgrading d7_image_settings
Upgrading d7_image_styles
Upgrading d7_node_settings
Upgrading d7_search_settings
Upgrading d7_system_authorize
Upgrading d7_system_cron
Upgrading d7_system_date
Upgrading d7_system_file
Upgrading d7_system_mail
Upgrading d7_system_performance
Upgrading d7_url_alias
Upgrading d7_user_flood
Upgrading d7_user_mail
Upgrading file_settings
Upgrading menu_settings
Upgrading search_page
Upgrading system_image
Upgrading system_image_gd
Upgrading system_logging
Upgrading system_maintenance
Upgrading system_rss
Upgrading system_site
Upgrading taxonomy_settings
Upgrading text_settings
Upgrading update_settings
Upgrading block_content_type
Upgrading d7_contact_settings
Upgrading block_content_body_field
Upgrading d7_custom_block
Upgrading d7_user_role
Upgrading d7_block
Upgrading d7_file
Upgrading user_picture_field
Upgrading user_picture_field_instance
Upgrading user_picture_entity_display
Upgrading user_picture_entity_form_display
Upgrading d7_field
Upgrading d7_node_type
Upgrading d7_comment_type
Upgrading d7_taxonomy_vocabulary
Upgrading d7_field_instance
Upgrading d7_user
Upgrading d7_node:page
Upgrading d7_node:story
Memory usage is 108.99 MB (85% of limit 128 MB), reclaiming memory. [warning]
Memory usage is now 108.83 MB (85% of limit 128 MB), not enough reclaimed, starting new batch [warning]
Upgrading d7_node:image
Upgrading d7_node:image_page

Fatal error: Call to a member function getFileUri() on null in C:\wamp64\www\REPOS\gsc\core\modules\image\src\Plugin\Field\FieldType\ImageItem.php on line 317
Drush command terminated abnormally due to an unrecoverable error. [error]
Error: Call to a member function getFileUri() on null in C:\wamp64\www\REPOS\gsc\core\modules\image\src\Plugin\Field\FieldType\ImageItem.php, line
317