@dj FOS (name for the FOG system that loads at that point) doesn’t need /sbin/mount.nfs
I just checked and tested and it all works fine in my environment.
Can you run mount -v | grep images on a system where you were able to mount the nfs share and take a screenshot/paste it here?
What Ubuntu version is the FOG server running btw?
Did you test the mount in FOS on a system that mount does work in a full linux distro?