Buffer/Base64 encoding issue in Node.js and Azure Web APP - node.js

Question

My code is working perfectly on local, the file being downloaded is never corrupt (I tried it dozens of time and the files always come complete), however when I run it on Azure (Web App); in a lot of times the returned file is corrupt (and with the wrong file size) - it's extremely random, sometimes it is returned fine and sometimes it is not.
My function that downloads the file from Azure blob storage is the following, the "setTimeOut" things are desperate attempts from my side to make it work without corruption
storageUtils.downloadBlobFromCloud = (subDirectory, fileName) => {
var dir = './temp';
var tempFilePath = dir + '/' + Date.now().toString() + '.temp';
console.log(tempFilePath)
var absolutePath = pathLib.resolve(tempFilePath);
if (!fs.existsSync(dir)) {
fs.mkdirSync(dir);
}
if (!fileName) {
return null;
}
return new Promise( (resolve, reject) => {
blobService.getBlobToLocalFile(
container,
`${subDirectory}/${fileName}`,
tempFilePath,
async function (error, serverBlob) {
if (!error) {
try {
let base64 = await fileStream(tempFilePath);
console.log("STREAMMMINNNGGGG")
setTimeout(() => {
resolve(base64);
}, 2000);
setTimeout(()=>{
console.log('deleting file')
fs.unlinkSync(tempFilePath);
},10000);
} catch (e) {
console.log('error1')
console.log(e)
reject(e);
}
} else {
console.log("fi error2")
console.log(error)
reject(error);
}
}
);
});
};
The stream function is
function fileStream( filePath) {
return new Promise((resolve, reject) => {
let buffers = [];
let myStream = fs.createReadStream(filePath);
myStream.on('data', (chunk) => { buffers.push(chunk); });
myStream.once('end', () => {
let buffer = Buffer.concat(buffers);
console.log("BUFFER SIZE " + buffer.length)
let base64 = buffer.toString('base64')
/* fs.writeFile('./temp/buffer.txt', base64, function (err) {
if (err) return console.log(err);
console.log(err)
}); */
resolve(base64);
});
myStream.once('error', (err) => {
reject(err);
});
});
}
the function that returns the response to client:
let downloadFile = async (directory, fileName, attempts) => {
attempts++;
let file = await storageUtils.downloadBlobFromCloud(directory, fileName);
if(attempts < 20 && !file) {
file = await downloadFile(directory, fileName, attempts);
}
return file;
}
server.post('/api/download-file', async function (req, res) {
try{
console.log(`downloading file ${req.body.fileName} ${req.body.directory}` )
let attempts = 0;
let file = await downloadFile(req.body.directory, req.body.fileName, attempts);
return res.json({ file });
}catch(error) {
console.log(error);
return res.json(error);
};
});
you may notice the commented "buffer.txt", I've checked the base64 code in the txt and it's indeed incomplete (ie. expecting 1.5MB file but it's 1MB) when the file is returned corrupt to client.
I am out of ideas, what am I doing wrong? and why things working perfectly on local but not on the cloud hosting?
NOTE: I have even did a side by side comparison between the base64 of the file downloaded fine vs when it's corrupt using a text checker tool, the two base64 blocs are identical for a large portion while scrolling down, then...it's blank for the "corrupt one", while the non-corrupt base64 is longer. As if it's something is "cutting" the base64 encoding.