I just ran a simple console app using FluentFTP and FileZillaServer to test the interaction between them.
I was able to transfer with no problem. I’m thinking the issue not with those but Duplicati is somehow ending the transfer before it is finished since adding my 3 second delay also makes Duplicati transfer the files correctly.
With the other thread about the same type of hash mismatch but for SMB I’m now wondering if there is an overall issue of backend transfers being stopped earlier at times.
I need to look into it further.