The previous post mentioned that the machine would not start properly, and how to get a serial console going. The reason for the failure was that the NFS share did not mount properly. Not entirely sure why, but this solved it;

In /etc/fstab, I had:

[2a01:4f8:nnn:nnn::nnn]:/srv /srv nfs defaults,noatime 0 0

Changing to this seems to have solved it. I’m no expert in NFS, but it works for me:

[2a01:4f8:nnn:nnn::nnn]:/srv /srv nfs rw,noatime,hard,intr,rsize=8192,wsize=8192,timeo=14 0 0