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Exporting sheet properties corrupts the file and it cannot be opened in Excel.
In the latest version we export:
<sheetPr>
<pageSetUpPr fitToPage="true" />
<tabColor rgb="FF92D050" />
</sheetPr>
Excel cannot read this and tries to recover the file unsuccessfully. This works in R3 2020.
The files are not properly recognized when the base64 string representing the exported XLS file is converted using https://base64.guru/converter/decode/file.
If an XLS file produced by MS Excel is converted with the same tool, it is generated with .bin extension.