Error combining readtable with basic true

Hello,

I am opening a decently large excel file using readtable. It works fine, however quite slowly if I use it normally and that is why i want to add the 'basic', true formating which has worked for me before, however when add the option I get the bug:

Unable to open file '*\references_update.xlsx' as a workbook. Check

that the file exists, read access is available, and the file is a valid spreadsheet file.

I know that the file exists, because I have checked and I just used it without the extra option. Any idea what is causing this and how to fix it?

Kind regards,

Benjamin