When saving a file from the ProtonMail App (MacOS) the app does not add a number to file when there are multiple of the same name

Every Monday morning I get a spreadsheet from one of my distributors that lists all items I have on pre and back order. I download that file, and then do my spreadsheet sorting. However, since I started to use the ProtonMail app on MacOS (vs in Safari) when I download the file, it gives an error that there is already a file by that name. When I save with Safari it adds a number to make it unique. I am unsure if this is a MacOS issue, or a ProtonMail app issue.