Files created on Windows 2019 NFS Server mounted to AIX server show up in Unix as 700 with group of "nobody"

Question

We just migrated to a Windows 2019 Server that is running NFS Server with an NFS drive shared out to and mounted to an AIX server. We are using Active Directory for Identity mapping, and LDAP on the AIX server. We have a common group that LDAP and Active Directory both recognize to control RW capability. When files get written to NFS from AIX, they take on the group as expected, but when a file gets written to NFS from the Windows side, they show up with 700 permissions and the group of "nobody." I checked user accounts and security groups by issuing Get-NfsMappedIdentity commands, and the NFS server always returns the correct Uid and Group information. All userids use uidNumber and Gid number and the username shows up on the file in AIX, but the group does not (shows as "nobody"). I have been working with IBM support, and this problem is clearly on the Windows side, but I have checked everything I can think of, and pretty much exhausted all possible avenues with IBM. What could possibly be preventing the group from being passed through to AIX?