Webform CLI fails on import CiviCRM content

This bug seems to require a lot of setup. Please update the issue summary with precise steps, starting with installing Drupal, to reproduce the bug, and include the YAML of a minimum example form.

It does require a bit of setup as we have a CiviCRM installation with a fair few custom fields. I'll try to create a 'minimum' example of where it will fail. One of the issues is that the you cannot tell from the logs exactly what the issue is. Of the various things that happen on the import, which one exactly triggers the problem, my guess is access to a custom field. In the meantime, I've solved the pressing issue from the other direction, i.e. giving overly permissive permissions to the anonymous user for the duration of the import. The Drupal permission required to be set is:
CiviCRM: all CiviCRM permissions and ACLs
Administer and use CiviCRM bypassing any other permission or ACL checks and enabling the creation of displays and forms that allow others to bypass checks.

If there is workaround for CiviCRM, I am going to mark this as won't fix