if you getting ORA-27054 error while using export option on network mounted disk then Mount the NFS mount point with the recommended options in the exact order specified in oracle documentation.[Document ID 781349.1]
# mount -F nfs -o rw,bg,hard,rsize=32768,wsize=32768,vers=3,forcedirectio,nointr,proto=tcp,suid <host name>:/<folder Name> /<Mount Folder to>
# mount -F nfs -o rw,bg,hard,rsize=32768,wsize=32768,vers=3,forcedirectio,nointr,proto=tcp,suid <host name>:/<folder Name> /<Mount Folder to>