Solution:
Root Cause: Co-Authoring Engine Sync Collisions When co-authoring is interrupted or two users save delta changes to the same block range simultaneously while a file is being restored, the OneDrive client (
FileCoAuth.exe) creates a branch file containing the machine name to prevent unmerged data loss.
Diagnostic Verification: 1 Check if Microsoft Office Co-Authoring is active: Open Word/Excel > File > Options > Save . Verify AutoSave is enabled.
2 Verify current file locks via PowerShell:
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powershell
Get-Process -Name "OneDrive", "FileCoAuth" | Format-Table Id, ProcessName, Path
Step-by-Step Fix: 1 Pause OneDrive synchronization on all affected endpoints:
Click OneDrive tray icon > Settings (Gear) > Pause syncing > Select 2 hours . 3 Locate the parent file, click the three dots (...), and select Version History .
4 Compare the timestamp and size of the conflicting versions. Select the authoritative version and click Restore .
5 Delete the duplicate file containing the appended computer name (e.g., Document-LaptopName.docx).
6 Resume synchronization on endpoints:
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cmd
%localappdata%\Microsoft\OneDrive\onedrive.exe
Prevention & Long-Term Monitoring: Ensure all desktop users update to current Microsoft 365 Apps to leverage modern differential sync. Instruct users to utilize Excel/Word Online when making concurrent structural edits to shared Workbooks.