[ubuntu] eCryptFS on Ubuntu 16.04 not auto mounting - timing issue ?

Recently rebuilt (not upgraded) a server from Ubuntu 14.04 to 16.04 and things seem to be working fairly well, with the exception of accessing two encrypted nfs shares.
If I manually mount them with mount -a everything is fine, no requests for passwords. so all the files including the fstab seem ok.
If I reboot the server the nfs shares mount ok but the encrypted shares do not. If I login and sudo mount -a manually then every thing is ok.
Looks like some type of timing issue, but I'm lost where to look.
I could create a systemctl script to force the mount but that seems like a bit of a bodge for something which should happen automatically.

My config is based on
https://help.ubuntu.com/lts/serverguide/ecryptfs.html

Any ideas?

Also is eCryptFS still the recommended way for NFS disk encryption under Ubuntu 16.04. If I need to change now would be a good time

Thanks