I’m not sure jumping into the live log after-the-fact is always reliable (and live log has other oddities).
However this would probably be in line with the backup itself being done, and verifications beginning.
It’s one overly-specific message for either choice, and it only works at certain limited spots in backup.
Choose ‘Stop now’ but status then shows ‘Stopping after current file’
So we’re still not sure what was going on. Best plan is if you can repro it on test backup with a log file.
Maybe we’ll dead-end at an SSH.NET limitation, or maybe there’s some Duplicati fix if a dev can help.