Sync to external: SSH OK but FTP gives error EACCES

[Chris Hayes]

I can sync using SSH to external card

I can sync using FTP to internal

But same sync using same FTP account to external card gives: 

     File transfe failed '[file name]':[file path] - open failed EACCES (permission denied)

file name and path the are source file details

Googling this gives a whole bunch of programming-level permissions  issues, so is this something that needs to be addressed in the FTP code, or can I do something as a user to make it work?

[Chris Hayes]

^ I add of course this is a Galaxy S5  - Lollipop, FolderSync 2.7.9.91