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