KB #1002: The remote server returned an error (500 + 409)

In case you experience one or both of the below errors, the site that are being backed up might be infected, or the built in antivirus has a false positive.

Error: The remote server returned an error: (500) Internal Server Error.

Error: The remote server returned an error: (409) Conflict.

Solution

Check whether items are infected, open OneDrive or Site which cannot be backed-up and try to download files manually. If an error: This file is compromised by malware appears the follow the Microsoft recommendations to solve this issue.

Cause

The Microsoft build in antivirus may detect infected files, and limit the access. If access is limited this service cannot process them.