The error probably appears because the “Excel command” tries to close the spreadsheet too quickly.
Try moving the “Excel command” into a separate module, then call the module using the “Call” action in the mode “Collect errors and continue”. In this case, the error will be ignored and the workflow won’t fail.
Alternatively, you can try to use PowerShell to run the script and insert a delay before closing the workbook. See an example (without a delay) here: Running Excel Macro in EasyMorph Project - #2 by dgudkov