A family of Microsoft spreadsheet software with tools for analyzing, charting, and communicating data.
Hello Guillaume,
Thank you for the update. As you said the issue does not occur in Print Preview and also that it appears only in old .xls files and not new ones, it seems to be some sort of a an issue with respect to the old files itself.
To resolve the issue you may only have to work-around the issue by copying and pasting the contents to a new Excel file.
Let us know if you need any other information or assistance.
Thank you.