You could certainly try. I think that’s an option on “repair” that used to be done automatically but now isn’t.
Release: 2.0.3.10 (canary) 2018-08-30 talks about it, and about its success rate. It didn’t help on my test.
C:\Program Files\Duplicati 2>Duplicati.CommandLine.exe help rebuild-missing-dblock-files
--rebuild-missing-dblock-files (Boolean): Rebuild dblock files when missing
If dblock files are missing from the destination, you can attempt to
rebuild them using local source data. However, since the local data may
have changed, it may not be possible to retrieve all the required data
and the process may be slow. Use this option to attempt to rebuild
missing dblock files.
* default value: false
C:\Program Files\Duplicati 2>
BTW your new reduced file size is a nice even binary value (multiple of 8 KB I think). Filesystem damage?