At least one case was fixed. You could try picking up v2.0.4.30-2.0.4.30_canary_2019-09-20 although the fix was actually first in 2.0.4.24 canary (which had serious issues – as did several successors). Note that return to beta will be awkward due to DB changes. In your DB folder there are backups of the old DB, but new files on the destination won’t be known to the DB if you put one back in use. Easiest path is to move forward. There might be an Experimental and/or Beta soon. You can change Settings away from Canary, after hand-picking one to test. Or at least don’t be the first to take new Canary unless you’re adventurous. Avoid 2.0.4.29, but 2.0.4.28 might be an option if you want a Canary with a little more age than 2.0.4.30…
CheckingErrorsForIssue1400 and FoundIssue1400Error test case, analysis, and proposal #3868 (Issue)
Fix for issue1400 #3872 (Pull request)
Sometimes one can also work around the problem (if this is the fixed problem of backing up a file while it’s changing) by excluding certain folders from the backup, for example the one with Duplicati’s databases is troublesome because the DB (especially its sqlite-journal file) changes due to backup, so triggers the bug. People who back up an entire drive or user profile may hit this. Not sure if this is your case, but it’s typical.
You can post a link to a DB bug report if you like. It might be possible to see if the problem is the fixed one.