heh.... I would be suspicious of the MS Excel too.... I use Linux/LibreOffice Calc....
But it doesn't look to me like you are doing anything "wrong" on the scope that would cause the corruption of the CSV file.
Have you installed the most recent firmware from the link that Warhawk provided above? The filename of the .gel file and the zip folder name are misleading, but once the firmware is installed the scope should report
Software Version 00.04.03.SP1
in the System Info screen.
If I were you I'd try the following three things:
First, install the new firmware and re-test. (ETA: Run the Self-Cal procedure after the new install, it may take a couple of tries to complete the self-cal successfully.)
If still fail...
Second, try a different USB stick and re-test.
If still fail...
Third, try a different spreadsheet program (or look at the CSV file in a text editor like NotePad)
If still fail... contact Rigol Tech Support....