Even its own specification cautions. Does that mean it’s a feature, not a bug? 
A comment on transfer modes. The stream transfer mode is
inherently unreliable, since one can not determine if the
connection closed prematurely or not.
I wonder if Duplicati should warn users more about FTP issues when they pick it?
Warning constantly would be annoying. Can Amazon Cloud Drive warn plan help?
As vendors change or disappear, having some good ways to warn would be good.