This probably has to do with the fact you are using no_root_squash (root= in /etc/dfs/dfstab) specified as the nfs client.
You are passing named user/group NFSv4 while in NFSv3 this was ID based.
So your options are to either specify NFSv3 or to ensure that the users/groups exist on both the cilent and server keeping their id's matched up.
If the names and groups are out of sync with the server/client you can have some wacky chown/chgrp issues.