This is actually a very well known issue with Synology, and potentially other NAS’.
Basically, the NFS side works perfectly, but FTP fails miserably.
This is a configuration issue of FTP on the NAS. What’s happening is the “fog” user defaults to a jailed root position.
In your case, /Volume1/NAS/data/images (or whatever the path is)
NFS side works as expected, but FTP fails because it’s Jailed to start at:
So basically, the mount point you have is set to /Volume1/NAS/data/images.
When FTP attempts to happen, It’s looking for /Volume1/NAS/data/images, but it’s really going to / which is the root of /Volume1
Basically ftp is looking for:
/Volume1/Volume1/NAS/data/images at that point, which obviously doesn’t exist.
One way you could try to fix it is create a symbolic link to /Volume1 in side of /Volume1/
This could be done with:
ln -s /Volume1 /Volume1/Volume1
It’s just a shot in the dark maybe?