Good news is that I have found a 'work-around'... the download error only seems to be coming up when my clients try to download multiple files from the OneDrive folder (they can download individual files, but that takes a long time when there are over 20 files), so...when I zipped the files before uploading them to OneDrive, my client was able to download the zipped file to easily drag and drop them to their computer from the downloaded zipped file.