When encountering unexpected data format changes in a Google Sheets automation script, I would start by examining the error messages and logs to understand what went wrong. This helps in pinpointing the exact issue. Next, I would use the Apps Script debugger to step through the code and inspect the variables to see where the script is failing. It's crucial to analyze the affected data in the spreadsheet by checking cell values, formatting, and the overall structure to identify any discrepancies. Implementing error handling is a key step to manage unexpected data formats and prevent the script from failing entirely. This could involve setting up try-catch blocks or validating data before processing it. Lastly, I would verify the script's assumptions about the data format against the actual data to ensure they align. If needed, I would adjust the script to accommodate any new data formats. This systematic approach helps in resolving the issue efficiently and ensures the automation process is robust and adaptable to changes.