samba - Jul 2016 - smbldap-passwd - Failed to modify SMB password: Insufficient access

Dear all,
I'm really stuck with an issue I hope you'll be able to help me solve:
whenever a user tries to change her password using the aforementioned
tool (smbldap-passwd) the Samba password doesn't get updated.

The user gets the following error:
  [got6924 at bezavrdatmaster02 ~]$ smbldap-passwd
  Identity validation...
  Enter your UNIX password:
  Changing UNIX and samba passwords for got6924
  New password:
  Retype new password:
  Failed to modify SMB password: Insufficient access at
/usr/sbin/smbldap-passwd line 182, <STDIN> line 3.

Please note that this was happening with version 0.9.10-6 of
smbldap-tools but also with version 0.9.11-1.

Running the same command as root works faultlessly.
Changing the password as an unprivileged user with smbpasswd also works fine.

Could you give me a hand to troubleshoot this thorny issue?

Thanks in advance and best regards,
Daniele Rispoli

Appendix A, other configuration details:
 - CentOS Linux release 7.2.1511 (Core)
 - 3.10.0-327.18.2.el7.x86_64
 - samba-common-tools-4.2.10-6.2.el7_2.x86_64
 - samba-client-libs-4.2.10-6.2.el7_2.x86_64
 - samba-client-4.2.10-6.2.el7_2.x86_64
 - samba-common-4.2.10-6.2.el7_2.noarch
 - samba-common-libs-4.2.10-6.2.el7_2.x86_64
 - samba-libs-4.2.10-6.2.el7_2.x86_64
 - samba-4.2.10-6.2.el7_2.x86_64
 - openldap-2.4.40-9.el7_2.x86_64