I installed Ubuntu 18.04LTS comming from 16.04LTS where I did not have this weird problem: If I mount a NFS share from a file server (i.e. Synology DS 418) Nautilus is not able to perform any write access to it (write, delete, make new directory,...). I can do all of this operations by using shell commands (touch, cp, mkdir...) in a terminal window. Also, nautilus can perform these actions if I start it with root privileges.
Even stranger is the following: even though nautilus cannot write into the mounted shares it is able to write into its subfolders. This bug seems to affect others as well: https://askubuntu.com/questions/1000973/nautilus-cannot-write-into-1st-directory-of-a-nfs-share
Ubuntu version: 18.04.1 LTS - amd64
Nautilus version: 1:3.26.4-0~ubuntu18.04.1
Thank you for your bug report. Can you write into that directory using the gio command line utility? Do you get any error in the journalctl log or in the nautilus UI when trying to copy to the base directory?