While trying to confirm who deleted a specific local user group we found the Credential>Reports>run page "Administrative Activities" report does not show the deletion of local user groups.
The Administrative Activities report is only for Credential Management reporting for credential management activities specifically which does not include local authentication user groups.
To find who deleted a specific access user group you will need to review the sessions>logs our your syslog reporting server if you have one configured.
The message in our session logs will look like this. PAM-CMN-1576: User group XXXXXXX successfully deleted