If all your files needed repair, my guess is there’s a communications issue somewhere between Duplicati and the Raspi destination.
You might want to try using the main menu “Restore” option and choose “Direct restore from backup files…” to see if you can restore from your destination.
To debug this, I’d recommend maybe changing your backup destination to a local folder and running a few backups. If they work fine, then we can be confident there’s nothing wrong with the local system / Duplicati installation.
After a few good local runs, try manually copying all the files to your Raspi destination and change the backup job to point there. If errors start getting reported, then we’ve isolated the problem to something outside your local computer.
If the remote files are of good quality (especially the dblock files), then a database REPAIR should do the trick. If it doesn’t, a database RECREATE (delete and create) will dump the local .sqlite file and rebuild it based on what can actually be obtained from the destination.
Of course if the destination files are not good, then your recreated database won’t do much for you (assuming it can be created at all).
Again, assuming the remove files are not damaged, the ARE useful for database repairs and restores. Even if you can’t repair / recreate the local database, you can still do a restore directly from the destination.