RHEL7: files created under incorrect permissions on nfs server

Issue

Files can randomly be created with incorrect permissions on NFS server, i.e. issuing a batch file creation operation from same client :

-rw-r--r--  1 user1 group1    0 Nov 27 09:09 testfile53
-rw-r--r--  1 user1 group1    0 Nov 27 09:09 testfile54
-rw-r--r--  1 user1 group1    0 Nov 27 09:10 testfile55
-rw-rw-r--  1 user1 group1    0 Nov 27 09:11 testfile56 <<---
-rw-r--r--  1 user1 group1    0 Nov 27 09:11 testfile57
-rw-r--r--  1 user1 group1    0 Nov 27 09:12 testfile58
-rw-r--r--  1 user1 group1    0 Nov 27 09:13 testfile59
-rw-r--r--  1 user1 group1    0 Nov 27 09:13 testfile60