Similar issues with some comments and troubleshooting ideas which the users didn’t clearly pursue:
Need help, backup failing to B2 cloud has an antivirus theory and a Process Monitor debugging idea.
Backup error - sftp - put has SftpPermissionDeniedException further down in all the stack traces.
The backend failure that I notice further down in all your stack traces is the following:
System.Net.WebException: The remote server returned an error: (403) Forbidden
Delete dlist file not found & exclude ~$ temporary files was my history of odd Google Drive 403 errors.
Generally such errors will be retried based on –number-of-retries, but eventually retries might exhaust.
Running a log at Retry level will detail each error, otherwise you might just see how the last one failed.