MongoDB misses saving data in a long period of time - node.js

Question

Good afternoon, I have a script which is receiving data from Binance API every 30 minutes and saves it in MongoDB specific database in different collections.
My MongoDB is installed on VPS. I'm connecting to it from my local computer.
Problem is that I leave my code to work constantly for ± 3 days and I receive that sometimes data did not save on specific collection or missed, etc. How I can configure my code or what can I do to create a perfect connection to save all data correctly.
Problem Explanation:
I have an array with
symbols=["ada","ae","kava","eth","etc","zrx","xzc","faq","gas","vfg","req"];
And when I leave the code for let's say 25 hours. I suppose to see 50 documents on every collection name.
But I receive that some collections got 48 documents saved instead of 50, some of them got 49, some of them got 50 like sometimes collections didn't save d properly.
FULLCODE HERE:
const { MongoClient } = require('mongodb');
const schedule = require('node-schedule');
const fetch = require("node-fetch");
const symbols=["ada","ae","kava","eth","etc","zrx","xzc","faq","gas","vfg","req"];
//a descriptive name helps your future self and others understand code easier
const getBTCData = async symbol => { //make this function accept the current symbol
//async/await lets us write this much nicer and with less nested indents
let data = await fetch(`https://api.binance.com/api/v3/klines?symbol=${symbol}&interval=30m&limit=1`).then(res => res.json());
const btcusdtdata = data.map(d => {
return {
Open: parseFloat(d[1]),
High: parseFloat(d[2]),
Low: parseFloat(d[3]),
Close: parseFloat(d[4]),
Volume: parseFloat(d[5]),
Timespan: 30,
}
});
console.log(btcusdtdata);
saveToDatebase(symbol, btcusdtdata);
//recursive functions are complicated, we can get rid of it here
//by moving the responsibility to the caller
};
//helper function for an awaitable timeout
const sleep = ms => new Promise(res => setTimeout(res, ms));
const j = schedule.scheduleJob('*/30 * * * *', async() => {
//expand this function to be responsible for looping the data
for (let symbol of symbols) {
//we can pass symbol to getBTCData instead of making it
//responsible for figuring out which symbol it should get
await getBTCData(symbol);
await sleep(8000);
}
});
//make this a helper function so `saveToDatabase()` isn't also responsible for it
const getDateTime = () => {
let today = new Date();
let date = today.getFullYear() + '-' + (today.getMonth() + 1) + '-' + today.getDate();
let time = today.getHours() + ":" + today.getMinutes() + ":" + today.getSeconds();
return date + ' ' + time;
};
const saveToDatebase = async(symbol, BTCdata) => {
const url = 'mongodb://username:password#server:port/dbname?retryWrites=true&w=majority';
let dateTime = getDateTime();
//use await here and below to vastly simplify this function
let db = await MongoClient.connect(url, { useUnifiedTopology: true });
const dbo = db.db('Crypto');
const myobj = { Name: symbol, Array: BTCdata, Date: dateTime };
await dbo.collection(symbol).insertOne(myobj);
console.log('1 document inserted');
db.close();
};
Goal: Solve the saving issue, I think it also can be possible something with VPS response itself. How can I maybe update my code that it looks cleaner and faster if possible?
Any suggestions or help really appreciated.