Hi,
Could you elaborate more on 'auth issues' that you are facing ? Errors/log/screenshot you could share ?
Also, have you had a chance to see this TR, this is a very well written KB, so much info is in there.
It's worth just reading the kerb auth process in there.
Kerberos, NFSv4, and LDAP in ONTAP
https://www.netapp.com/us/media/tr-4073.pdf
Also give us this:
centos kernel version? [uname -a]
nfs-utils package version? [rpm -qa nfs-uti*]
Thanks!