I can confirm this issue, on Ubuntu Bionic - server is 4.15.0-43-generic, client is 4.15.0-45-generic. Server filesystem is ZFS (using nfs-kernel-server for export). Mounting with vers=4.1 works around it as noted above.
I can confirm this issue, on Ubuntu Bionic - server is 4.15.0-43-generic, client is 4.15.0-45-generic. Server filesystem is ZFS (using nfs-kernel-server for export). Mounting with vers=4.1 works around it as noted above.