Steps to Reproduce

Do the following

• Perform the suggested resolution in this KB. Make sure that 'Internal with LDAP Authentication' directory is positioned at the top.

Result

When we upgrade from osuser, it treats all users and groups as internal users.
All the existing Confluence internal users belong to internal directory (the directory_id of the users/groups is pointing to INTERNAL directory).
So when you later add LDAP for Authentication, this creates a new directory. Any users created in this directory will not have the previous group mappings.