SFTP resume after abort/error

Hi there,
I have been wondering about the following behavior for a while.

When downloading via SFTP, if I click Abort voluntarily, the partially downloaded file(s) remains in the destination. That's great, it lets me Resume later if needed.

But if I click Abort because of an error (for instance, the internet connection was reset, and Opus gives a connection error), the partially downloaded file disappears (on the local, Windows side), so there is no chance of resuming.
This happens so often that I have come to rely on this workaround: whenever clicking Abort, I first make a copy of the partial download; when I click Abort, the partial download disappears, so I rename the copy (removing "(Copy)" ). Then I try downloading again, and Opus offers to resume.

The best way I can think of duplicating that would be to switch your modem on and off in the middle of a download.

Thanks in advance for any thoughts.