Node Async ReadStream from SFTP connection

So I'm creating a class and ultimately want to create a method that takes a file on an SFTP server and produces a readstream that can be piped into other streams / functions. I'm most of the way there, except my readStream is acting strangely. Here's the relevant code:

const Client = require('ssh2').Client,
      Readable = require('stream').Readable,
      async = require('async');

/**
 * Class Definition stuff
 * ......
 */

getStream(get) {
    const self = this;
    const rs = new Readable;
    rs._read = function() {
        const read = this;
        self.conn.on('ready', function(){
            self.conn.sftp(function(err,sftp) {
                if(err) return err;

                sftp.open(get, 'r', function(err, fd){
                    sftp.fstat(fd, function(err, stats) {

                        let bufferSize = stats.size,
                            chunkSize = 512,//bytes
                            buffer = new Buffer(bufferSize),
                            bytesRead = 0;

                        async.whilst(
                            function () {
                                return bytesRead < bufferSize;
                            },
                            function (done) {
                                sftp.read(fd, buffer, bytesRead, chunkSize, bytesRead,
                                function (err, bytes, buff) {
                                    if (err) return done(err);
                                    // console.log(buff.toString('utf8'));
                                    read.push(buff);
                                    bytesRead += bytes;
                                    done();
                                });
                            },
                            function (err) {
                                if (err) console.log(err);
                                read.push(null);
                                sftp.close(fd);
                            }
                        );

                    });
                });
            });
        }).connect(self.connectionObj);
    }
    return rs;

}

Elsewhere, I would call this method like so:

let sftp = new SFTP(credentials);

sftp.getStream('/path/file.csv')
.pipe(toStuff);
.pipe(toOutput);

So, long story short. During the SFTP.read operation read.push(buff) keeps pushing the same first part of the file over and over. However, when I console.log(buff) it correctly streams the full file?

So I'm scratching my head wondering what I'm doing wrong with the read stream that it's only pushing the beginning of the file and not continuing on to the next part of the buffer.

Here's the docs on SSH2 SFTP client: https://github.com/mscdex/ssh2-streams/blob/master/SFTPStream.md

I used this SO question as inspiration for what I wrote above: node.js fs.read() example

via AdamPat