Address fields disabled when checking out as admin

When using address fields with Drupal Commerce am finding that when you check out as an admin user the fields are disabled.

This is not usually the case as I've created many DC sites using address fields and have never encountered this before.

Thought it may be an issue with the order so cancelled the order and created a new one, same issue.

Logged out and checked out as an anonymous user or non-admin user and the fields are enabled.

See attached image of disabled fields. BTW, can still submit the form with no validation errors even though the values for the address fields that are required are empty.