Excel files uploaded to Dropbox using Node.js SDK are invalid

I am trying to upload Excel files to Dropbox using the Node.js SDK (https://github.com/dropbox/dropbox-sdk-js). The files are received from JsReport, and are saved correctly when saved to my local disk. However, when uploading to Dropbox, the files end up long strings instead of Excel files.

The body in this case is a string that gets encoded to base64. The filename is speedtest_daily_2021-01-15_test26.xlsx.

This line writes the file successfully to my local drive:

fs.writeFileSync(*filename*, body, {encoding: 'base64'});
This is the code I'm using to upload the file to Dropbox:

body = Buffer.from(body).toString('base64');

dbx.filesUpload({ contents: body, path: saveLocation + `/` + filename })
.then((response: any) => {
console.log(`Saved file "${filename}" to Dropbox folder ${saveLocation}`);
}).catch((uploadErr: DropboxError<files.UploadError>) => {
console.log(uploadErr);
});
This is how the Excel file should look, and looks on my local:

This is what happens when I open the Dropbox Excel file:

This is how the Dropbox file looks when I open it up in a text editor:

I've tried various encoding combinations for Dropbox but none of them seem to work. tell me what i should do