It sounds like you got some damage in the actual backup files. This is what 2.0.5.1 avoids much better, however it’s not any better at reading backups that already got damage. Is start-over too unattractive?
You already know how to delete the database. Deleting the destination will let you backup current files, however old file versions will be lost. If you want them, it will likely require very detailed technical work.
If you’re unsure, you could copy your old backup off, just in case you need something. There is a tool:
Duplicati.CommandLine.RecoveryTool.exe
This tool can be used in very specific situations, where you have to restore data from a corrupted backup.
however it’s probably not something you want to be running all the time, because it’s command line.
My guess at what you’re seeing is this now-fixed issue:
CheckingErrorsForIssue1400 and FoundIssue1400Error test case, analysis, and proposal #3868
Backup fails with CheckingErrorsForIssue1400 and FoundIssue1400Error (as a pair), or maybe "Detected non-empty blocksets with no associated blocks!" appears, but other two may be in log too if one looks. There have been numerous forum and some GitHub reports on both issues, with little progress beyond thinking a file changing during backup causes it. The test here was using the following writer.bat script:
Do you think you might have some files that are growing at time of backup? If so, that could cause this. Windows can use snapshots, but this is not often an option on Linux due to lack of setup at installation.