Discord.js level system not leveling up as XP keeps going - mongodb

Question

Coding a discord.js bot using WOK's tutorials, made a basic leveling system, I will add more features to it in the future, and the code is working mostly, except that the level doesn't update when the XP reaches the right value. Every message takes up 10 XP and the amount of XP needed to level up is (level number * 100) e.g. level 1->2 = 100, level 2->3 = 200 etc.
The code works and doesn't return any errors until when I type a certain amount of messages that should get me to the next level, i get this error: drainWaitQueue(topology[kWaitQueue], new MongoError('Topology is closed, please connect'));
And the level-up message from the bot doesn't send and the mongo database just keeps adding XP instead of resetting it to 0 and adding 1 level.
Here is my code:
const mongo = require('./mongo')
const profileSchema = require('./schemas/profile-schema')
const Discord = require('discord.js')
module.exports = (client) => {
client.on('message', (message) => {
const { guild, member } = message
addXP(guild.id, member.id, 10, message)
})
}
const getNeededXP = level => level * 100
const addXP = async (guildId, userId, xpToAdd, message) => {
await mongo().then(async (mongoose) => {
try {
const result = await profileSchema.findOneAndUpdate({
guildId,
userId,
}, {
guildId,
userId,
$inc: {
xp: xpToAdd,
},
}, {
upsert: true,
new: true,
})
let { xp, level } = result
const needed = getNeededXP(level)
if (xp >= needed) {
++level
xp -= needed
const levelUpEmbed = new Discord.MessageEmbed()
.setTitle('**NEW LEVEL REACHED**')
.setDescription(`You are now level ${level} with ${xp} experience! You now need ${getNeededXP(level)} XP to reach the next level!`)
message.channel.send()
await profileSchema.updateOne({
guildId,
userId
}, {
level,
xp
})
}
} finally {
mongoose.connection.close()
}
})
}
module.exports.addXP = addXP
Here is the schema for the mongo database, which also includes a coins amount for an economy system (the economy system works perfectly fine):
const mongoose = require('mongoose')
const reqString = {
type: String,
required: true
}
const profileSchema = mongoose.Schema({
guildId: reqString,
userId: reqString,
coins: {
type: Number,
default: 0,
},
xp: {
type: Number,
default: 0
},
level: {
type: Number,
default: 1,
}
})
module.exports = mongoose.model('profiles', profileSchema)
Please advise.