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'

Issue Recurrence - July 20, 2026 Veeam Technical Support is tracking several recent cases where the issue reported in this article is occurring. This recurrence is under investigation, and this notice will be updated as further information becomes available. Update - July 27, 2026 To remediate th...