Set APP_ENV=prod.

As 'admin' User:

• Add Section 'Admin Only' admin_only
• Change Role 'Editor' Assignments to:
  Role 'Editor' Assignments

      Editors	: Subtree: /Media
      Editors	: Section: Standard
  

• Add field to Content Type folder:
  Content Type folder

      identifier: relations
      type: ezobjectrelationlist
  

• Add User to User Group 'Editors':
  User test.editor

      login: test.editor
      email: admin@link.invalid
      password: Publish2024!
  

• Add Content below "Ibexa Platform" folder:
  1. Folder A - Admin Section -> set Section to 'Admin Only'
  2. Folder B -> add Relation to 'Folder A - Admin Section'

Use Migration 01_test_duplicate_relations.yamlon a fresh Ibexa Experience 4.6.7 installation to avoid previous steps !  

As 'test.editor' User:

• Edit and publish 'Folder B' 

As 'admin' User:

• Check Relation tab for 'Folder B'

Result:
The identical Relation is shown multiple times.
ezcontentobject_link table has multiple entries having identical values for:

contentclassattribute_id
from_contentobject_id
from_contentobject_version
relation_type
to_contentobject_id

Note:
When Content is changed as 'admin' User you will get one relation as expected.