Node server is getting down with Error: write after end

We are streaming files from s3, its running well but sometime (randomly in few days) its gives error and node instance is getting down. our code is

s3Utils.headObject(assetId, function (err, metadata) {
        if (err && err.code === 'NotFound') {
          console.log("file not found on s3: ", assetId) ;

          res.send({"success":false, "message":"file not found on s3: "+ assetId});
        } else {
          var download_file_name = assetId;
          if(metadata.Metadata && metadata.Metadata.filename) {
            download_file_name = metadata.Metadata.filename;
          }
          if(metadata.ContentLength) {
            res.setHeader('Content-Length',metadata.ContentLength);
          }

          res.setHeader('Content-disposition', 'attachment; filename=' +download_file_name);
          res.attachment(download_file_name);

          var fileStream = s3Utils.getObjectAsReadStream(assetId);
          fileStream.pipe(res);
        }
      });

we are getting below error in logs

    events.js:154
      throw er; // Unhandled 'error' event
      ^

Error: write after end
    at writeAfterEnd (_stream_writable.js:166:12)
    at PassThrough.Writable.write (_stream_writable.js:211:5)
    at IncomingMessage.ondata (_stream_readable.js:536:20)
    at emitOne (events.js:90:13)
    at IncomingMessage.emit (events.js:182:7)
    at IncomingMessage.Readable.read (_stream_readable.js:368:10)
    at flow (_stream_readable.js:751:26)
    at resume_ (_stream_readable.js:731:3)
    at _combinedTickCallback (internal/process/next_tick.js:74:11)
    at process._tickDomainCallback (internal/process/next_tick.js:122:9)

Server is getting down after this error. Please suggest.

via A_J