Download dropbox images to Netlify build folder

I'm trying to retrieve images from my dropbox folder into my Jekyll build on Netlify, but the images are unreadable with the following code. I think that I'm using the wrong conversion for the contents.

dbx
  .filesListFolder({ path: "/images" })
  .then(response => {
    response.entries.forEach(entry => {
      const { name, path_lower } = entry;

      if (entry[".tag"] === "file") {
        dbx
          .filesDownload({ path: path_lower })
          .then(data => {
            const filename = path.resolve(IMAGES_DIR, name);
            const filecontents = data.fileBinary.toString("base64");

            fs.outputFile(filename, filecontents).catch(error => {
              if (error) {
                return console.log("Error: file failed to write", name, error);
              }
            });
          })
          .catch(error => {
            console.log("Error: file failed to download", name, error);
          });
      }
    });
  })

Any help will be much appreciated. Thanks.