OneDrive / SharePoint Backup Fails with "Error: Invalid MIME content-length header encountered on read."

Challenge A backup job for OneDrive or SharePoint items processed by Veeam Backup for Microsoft 365 fails when attempting to download certain item versions, displaying the following error: Invalid MIME content-length header encountered on read Cause The issue is related to the download process us...

SharePoint or OneDrive Backup fails with 'Cannot complete this action'

This article has been updated to document the July 20, 2026, occurrence of this issue. Information regarding the February 2026 occurrence can be found in the More Information section at the very bottom of this article. Challenge A backup attempt for SharePoint Online and OneDrive objects may fail...