Anyway I decided to try using nfc to save snapshots to my NAS due to erratic results I've been getting with ftp.
I have found that when setting up the storage destination and clicking on test, the result is always the same, "NFC connection failed". That message appears to be wrong because all my cameras are now saving snapshots as expected.
I'll have to go back to ftp though because of the crazy file structure that is created using the nfc connection, a new folder for every minute.
It would be nice if after several years of having this problem, the cameras could be made to save to a NAS using a sensible file structure. A potetnial 1440 folders being created for every day is too many!
p.s. I don't quite know why it's called nfc in the settings. To me that's a communication method used by smart phones. It should be nfs (network file system)