Custom Document Properties can create invalid files.
The following trivial code generates a corrupted file. The same works with the previous 3.0.x version. In attach you can find the file. The file had some macros and sheets but for privacy i deleted them and obtained basically a blank file that still generates a corrupted file. I believe there is some hidden configuration in the file that breaks the save with the new package version. ```markdown from openpyxl import load_workbook, __version__ print(__version__) wb = load_workbook("input.xlsm", keep_vba=True) wb.save(filename = "output.xlsm") ``` Thank You, Lorenzo [input.xlsm](/uploads/45fa33bb902874927b74c73bf2638a77/input.xlsm)
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