For your decision, note that Canary has the latest bug fixes and features, but also may have new bugs, so using it for valuable backups is a judgment call. Also, newer Duplicati can have database version updates, meaning going back to the old version can be awkward (one way is by the backup file that’s made for you).
The error is probably not version-dependent. That’s not known certainly, but I haven’t heard of any such fix.
–log-file at –log-file-log-level=retry is probably a good place to start. Live log is easier to run, harder to post. I’m not sure how much activity is before error, but even a large log can be turned into a .zip file and posted. Small amounts can be pasted into the forum with three backticks (```) above and below to stop formatting.
Thanks for any light you can give on what goes on during a failed run. I hope heavy collecting isn’t needed. It’s a shame the temporary file names are all alike, so it’s hard to know what that missing file was used for.