Assuming you are using Generic (GBM) this is usually caused by kodi crashing. If ssh is enabled login should still be possible. With adding systemd.debug_shell to the kernel command line a debug shell can be reached at console 3 with Alt-F3 as long kodi is not running.
If you are using the overlay parameter the message is caused by this mkdir. Please check the access rights of 172.16.3.4:/mnt/media/storage
Yes it is Generic. If I drop KERNEL/SYSTEM back to the LE 12 or LE `13 before Dec 6th the mkdir works so what access right would have changed?
Thanks though I now can drop to the shell with ALT-F3 and can see that when it works mount has
172.16.3.4:/mnt/media/storage/1002b58608ea on /storage type nfs (rw,noatime,vers=3,rsize=32768,wsize=32768,namlen=255,hard,nolock,proto=tcp,timeo=600,retrans=2,sec=sys,mountaddr=172.16.3.4,mountvers=3,mountproto=tcp,local_lock=all,addr=172.16.3.4)
and in the newest version the line is the same but that rw turns to ro but I can see existing files.