Invalid image from a base64 string

Question

I receive an image in base64 from my nodejs express server like so:

  fs.writeFileSync("image.png", tensor);
  const readStream = fs.createReadStream('image.png');
  readStream.pipe(res);

This is what I see in the console on the client.

Then I try to download it like this:

function downloadBase64File(contentType, base64Data, fileName) {
  const linkSource = `data:${contentType};base64,${base64Data}`;
  const downloadLink = document.createElement("a");
  downloadLink.href = linkSource;
  downloadLink.download = fileName;
  downloadLink.click();
}

downloadBase64File("image/png", response.data, "image.png");

However, the downloaded image is corrupt, even though the size seems to be ok ~7.3MB:

What can be wrong here? How to send a base64 image to the client and download it?

Thank you