After test running the convert_entity_media_embed_entities queue dev environment content, a database search revealed one field value with a <drupal-entity> tag that was not converted to media. Investigation revealed that the value in question had a new line "\n" character within the tag markup. New lines are not matched by the /<drupal-entity(.*)data-entity-type="media"(.*)>( )?<\/drupal-entity>/ regular expression pattern.
Not sure whether having a new line in this markup is an edge case or unexpected user input at some point.
<drupal-entity> tags.Change the pattern to include 's', so that '.' matches new lines. In doing this, the pattern also needs to be changed to not be greedy: '/<drupal-entity(.*?)data-entity-type="media"(.*?)>( )?<\/drupal-entity>/s'
Needs review
1.0
Code
Put up an MR with the regexp change that seems to work for our project, in case it's useful to others.