Excel was able to open the file by repairing or removing the unreadable content. Removed Records: Formula from /xl/calcChain.xml part (Calculation properties) / Repaired Records: Cell information from /xl/worksheets/sheet1.xml part

What's actually wrong

These cryptic lines are Excel's repair log telling you exactly which internal XML part it fixed or deleted, and they range from harmless to serious. 'Removed Records: Formula from /xl/calcChain.xml' is almost always harmless — calcChain only stores the order formulas recalculate in, and Excel rebuilds it automatically. 'Repaired Records: Cell information' or 'Format from /xl/styles.xml' usually means values survived but some formulas or formatting were altered. 'Removed Part' on a worksheet, sharedStrings.xml, or pivot/VBA parts means real content was deleted — sharedStrings holds every text cell in the workbook, so its removal can blank out all text. Files written by scripts and export tools (openpyxl, EPPlus, Alteryx, Apache POI) are frequent culprits.

Free fixes — try these first

1. Triage by the part named in the log. If it only names calcChain.xml: nothing is lost — press Ctrl+Alt+F9 to force a full recalculation, Save As a new name, done. If it names a worksheet, sharedStrings, pivot or vbaProject part, treat it as real data loss and do NOT overwrite the original file.
2. Restore a previous version. If the file lives on OneDrive/SharePoint: right-click it online → Version history → restore the last version that opened cleanly. On Windows, right-click the file → Restore previous versions.
3. Compare repaired vs. original. Save the repaired copy under a new name, then check the areas the log mentioned (Name Manager for removed named ranges, key formula cells) against a backup or a colleague's copy so you know precisely what to re-enter.
4. Inspect the XML yourself. Copy the original file, rename the copy to .zip, extract it, and open the part named in the log (e.g. xl/worksheets/sheet1.xml) in Notepad++. The full error in the repair XML gives a line and column number — often it's a single illegal character you can delete before re-zipping.
5. If a script or tool generated the file (pandas, EPPlus, Alteryx, an ERP export), the generator is writing invalid XML — regenerate the file and report the bug; opening and re-saving via LibreOffice Calc also produces a clean copy Excel accepts.

If the free fixes fail

When the log says 'Removed Part' for a worksheet or sharedStrings.xml, Excel has already amputated data rather than repaired it — and it did so on the copy it opened, while the original file may still hold recoverable content. Our analyzer parses that original without Excel's all-or-nothing rules, tells you which specific records are intact, and shows the recovery percentage up front.