Metatag images don't work anymore after updating
This issue is documented here : https://www.drupal.org/project/metatag/issues/2994433

For the moment (21/09/18), there are two solutions :


add :entity:url at the end of the token
downgrade to Metatag 1.5 instead 1.6


Using first solution, change [node:field_image_article:entity:field_image] for [node:field_image_article:entity:field_image:entity:url] did the job for me.