Hello,
Thank you so much for posting here.
According to our description, it could show all the members of AD groups using AD Users and Computers, but it only shows parts of members using Softerra. So sorry that we are not familiar with Softerra. Have we tried ldp.exe?
Besides, according to my reseach, Most methods do not reveal membership in the "primary" group. For most users, the "primary" group would be "Domain Users". Specifically, the memberOf attribute of user objects, and the member attribute of group objects, never reveals "primary" group membership.
For more information, we could refer to:
https://social.technet.microsoft.com/Forums/Sharepoint/en-US/373febac-665c-494d-91f7-834541c74bee/cant-get-all-member-objects-from-domain-users-in-ldap?forum=winserverDS
Hope the information is helpful. For any question, please feel free to contact us.
Best regards,
Hannah Xiong