Hi James
I'm new here but from what I've gathered running a calibre library on a network share is not advised and you will have issues sooner or later.
So, given you understand the risks, how are you doing the mappings? are you mounting the nas shares in /etc/fstab so they mount on boot?
some resources to help set this up if not
https://timlehr.com/auto-mount-samba...stab-on-linux/
https://www.techrepublic.com/article...hare-on-linux/
when mounting shares configured in fstab manually, e.g. if they get disconnected and you dont want to reboot the device then verbose switch (-v) might help identify mount failure reason, e.g.
mount -av
hth, jon