Forum Discussion
Has anyone seen Excel workbooks become corrupt after using M365 Copilot to summarize data?
We’ve run into an issue twice where a user opened an existing Excel sales workbook, used Microsoft 365 Copilot in Excel to summarize/analyze the data, received the response successfully, and then later could no longer open the original workbook because Excel reported it as corrupt. Internally, this has been reported as happening on some files but not all, and it has occurred twice so far.
I’m trying to determine whether this is:
- a known issue with Copilot in Excel
- a workbook-specific problem
- related to file location/sync/versioning
- or something tied to workbook structure
I did find public reports of related Excel Copilot issues — including Copilot crashing in Excel, failures that seem specific to certain workbooks, and Copilot-created Excel files being reported as invalid/corrupt — but I have not yet found a clear Microsoft-hosted thread describing this exact scenario with the original existing workbook becoming corrupt after summarization.
If anyone has seen this, I’d appreciate any insight on:
- whether Microsoft has acknowledged a known issue
- whether this points to specific workbook features/structures
- whether there are logs or diagnostics that help isolate root cause
- whether there are best practices to reduce the risk
1 Reply
Hi, I would preserve both affected files before testing further. If they are in SharePoint or OneDrive, restore a previous version and compare the workbook structure, size, external links, macros, data model, and coauthoring state. Update Office, then try Excel's Open and Repair on a copy. Reproduce only with a sanitized workbook and version history enabled. Collect the Office build, Copilot interaction time, file location, and any Excel event or diagnostic logs, then open a Microsoft 365 support case. Until the cause is known, have users work on copies of important workbooks before asking Copilot to analyze them.
