rpc.idmapd logs some unknown messages "nss_getpwnam: name 'xxxx' domain 'localdomain': resulting localname '(null)" and "nss_getpwnam: name 'xxxx' does not map into domain 'localdomain'"

Issue

• On NFS server, the following messages are observed in /var/log/messages file for some unknown reason when I move some file from one NFS mount to another NFS mount.

Jun 23 19:37:01 host01 daemon.warning: rpc.idmapd[xxxxx]: nss_getpwnam: name 'xxxx' domain 'localdomain': resulting localname '(null)'
Jun 23 19:37:01 host01 daemon.warning: rpc.idmapd[xxxxx]: nss_getpwnam: name 'xxxx' does not map into domain 'localdomain'

• Looking at rpc.idmapd debug logs, I can see some additional messages that imply some unknown errors are encountered:

Jun 22 19:41:37 host01 daemon.warning: rpc.idmapd[xxxxx]: Server : (user) id "xxxx" -> name "user@localdomain"
Jun 22 19:41:37 host01 daemon.warning: rpc.idmapd[xxxxx]: nfsdcb: authbuf=10.10.10.0/25 authtype=group
Jun 22 19:41:37 host01 daemon.warning: rpc.idmapd[xxxxx]: nfs4_gid_to_name: calling nsswitch->gid_to_name
Jun 22 19:41:37 host01 daemon.warning: rpc.idmapd[xxxxx]: nfs4_gid_to_name: nsswitch->gid_to_name returned 0
Jun 22 19:41:37 host01 daemon.warning: rpc.idmapd[xxxxx]: nfs4_gid_to_name: final return value is 0
Jun 22 19:41:37 host01 daemon.warning: rpc.idmapd[xxxxx]: Server : (group) id "xxxx" -> name "user@localdomain"
Jun 22 19:41:37 host01 daemon.warning: rpc.idmapd[xxxxx]: nfsdcb: authbuf=10.10.10.0/25 authtype=user
Jun 22 19:41:37 host01 daemon.warning: rpc.idmapd[xxxxx]: nfs4_name_to_uid: calling nsswitch->name_to_uid
Jun 22 19:41:37 host01 daemon.warning: rpc.idmapd[xxxxx]: nss_getpwnam: name 'xxxx' domain 'localdomain': resulting localname '(null)'
Jun 22 19:41:37 host01 daemon.warning: rpc.idmapd[xxxxx]: nss_getpwnam: name 'xxxx' does not map into domain 'localdomain'
Jun 22 19:41:37 host01 daemon.warning: rpc.idmapd[xxxxx]: nfs4_name_to_uid: nsswitch->name_to_uid returned -22
Jun 22 19:41:37 host01 daemon.warning: rpc.idmapd[xxxxx]: nfs4_name_to_uid: final return value is -22
Jun 22 19:41:37 host01 daemon.warning: rpc.idmapd[xxxxx]: Server : (user) name "xxxx" -> id "xxxx"

• I believe there is nothing wrong with NFSv4 ID name mapping as 'Domain' is properly set in /etc/idmapd.conf on both NFS server and client:

# The following should be set to the local NFSv4 domain name
# The default is the host's DNS domain name.
#Domain = local.domain.edu
Domain = localdomain

• What do these messages mean?

• Do these messages indicate some problematic condition happening on the NFS server or client which requires some manual intervention to resolve the issue?