String of Errors on backup with seemingly little explanation

Any idea how it helped? Did it seem likely that first destination filled?

Error message about remote volumes marked as deleted had workaround of version deletes.
That’s a little surprising to me, as the failure comes from a surprise in the version deletions…

Getting more information would be helpful, so that the problem can be understood then fixed.
Unfortunately it’s not guaranteed easy. Some methods are kind of technical. One such one is:

Look at Database screen to find its path. Make a copy or be riskier and open it read-only with
DB Browser for SQLite that you install. State in Remotevolume table might be of interest.

File states can also be found by adding upload-verification-file advanced option which uploads a duplicati-verification.json file which has the destination files and their states.
There’s not anything particularly secret about the information there. You can look, zip, post it.

Another way is to run Create bug report which (maybe slowly) makes a sanitized DB copy. Frequently a job DB is bigger than one can post, so you’d use cloud storage, and share a link.

Preferably there will be developer help interpreting. If you like, you can probably avoid issues temporarily by changing retention policy to keep all versions, and put the setting back later on.

Maybe the dev can give thoughts. Yours had more volumes than filesets. This went other way: