Keyboard event fires twice even when using !event.repeat

I am preeeeeeeety sure this is a severe javascript bug, I was able to reproduce the problem, for example you press and keep holding Q and then you press and keep holding W, then you release only Q while still holding W, it will fire a W event.

Here's what I did, I create an array of pressed keys, and the respective pitch can only be played again if the key is release, and on key up I remove the key from the pressed key array:

I also add LowerCase logic because if caps lock was activated the piano wouldn't work

let notes = document.getElementsByClassName("note");
let soften = document.getElementById("soften");
let sustain = document.getElementById("sustain");
let keyAssist = document.getElementById("key-assist");
let piano = document.getElementById("piano");
let context = new (window.AudioContext || window.webkitAudioContext)();
let keysMap = new Map([
  ["q", "C3"],
  ["2", "Db3"],
  ["w", "D3"],
  ["3", "Eb3"],
  ["e", "E3"],
  ["r", "F3"],
  ["5", "Gb3"],
  ["t", "G3"],
  ["6", "Ab3"],
  ["y", "A3"],
  ["7", "Bb3"],
  ["u", "B3"],
  ["i", "C4"],
  ["9", "Db4"],
  ["o", "D4"],
  ["0", "Eb4"],
  ["p", "E4"],
  ["[", "F4"],
  ["=", "Gb4"],
  ["]", "G4"],
  ["a", "Ab4"],
  ["z", "A4"],
  ["s", "Bb4"],
  ["x", "B4"],
  ["c", "C5"],
  ["f", "Db5"],
  ["v", "D5"],
  ["g", "Eb5"],
  ["b", "E5"],
  ["n", "F5"],
  ["j", "Gb5"],
  ["m", "G5"],
  ["k", "Ab5"],
  [",", "A5"],
  ["l", "Bb5"],
  [".", "B5"],
  ["/", "C6"],
]);

// load all audio files when page loads so that when the user presses keys the sounds start on time
// store buffers in array to access piano sounds when user presses a key
let buffers = [];
window.addEventListener("load", function () {
  for (let i = 0; i < notes.length; ++i) {
    let request = new XMLHttpRequest();
    request.open("GET", "./audio/" + notes[i].id + ".mp3");
    request.responseType = "arraybuffer";
    request.onload = function () {
      let undecodedAudio = request.response;
      context.decodeAudioData(undecodedAudio, (data) => (buffers[notes[i].id] = data));
    };
    request.send();
  }
});

function isValidInput(input) {
  return keysMap.has(input) === true;
}

function playNote(pitch) {
  let playSound = context.createBufferSource();
  let gainNode = context.createGain();
  playSound.buffer = buffers[pitch];

  if (soften.checked === true) {
    gainNode.gain.setValueAtTime(0.4, context.currentTime);
    gainNode.gain.exponentialRampToValueAtTime(0.85, context.currentTime + 0.35);
  } else {
    gainNode.gain.setValueAtTime(1.5, context.currentTime);
  }

  playSound.connect(gainNode);
  gainNode.connect(context.destination);
  playSound.start(context.currentTime);

  if (sustain.checked === false) {
    gainNode.gain.exponentialRampToValueAtTime(0.001, context.currentTime + 3);
  }
}

var currentlyPressedKeys = []; //<========== ADDED HERE ###########

// Keyboard Input
document.addEventListener("keydown", function (e) {
  let key = e.key.toLowerCase();

  if (!e.repeat && isValidInput(key) && !currentlyPressedKeys.includes(key)) { //<========== ADDED HERE ###########
    let pitch = keysMap.get(key);
    playNote(pitch);
    document.getElementById(pitch).classList.add("key-bkg-color");
    currentlyPressedKeys.push(key); //<========== ADDED HERE ###########
  }
});

document.addEventListener("keyup", function (e) {
  let key = e.key.toLowerCase();

  let pitch = keysMap.get(key);

  if (document.getElementById(pitch)) {
    document.getElementById(pitch).classList.remove("key-bkg-color");
  }
  currentlyPressedKeys = currentlyPressedKeys.filter((pressedKey) => pressedKey != key); //<========== ADDED HERE ###########
});

// Mouse Input
let isDown;
document.activeElement.addEventListener("mousedown", function (e) {
  if (e.target.tagName === "BUTTON") {
    playNote(e.target.id);
    e.target.classList.add("key-bkg-color");
    isDown = true;
  }
});

document.activeElement.addEventListener("mouseup", function (e) {
  e.target.classList.remove("key-bkg-color");
  isDown = false;
});

piano.addEventListener("mouseover", function (e) {
  if (e.target.tagName == "BUTTON" && isDown === true) {
    playNote(e.target.id);
    e.target.classList.add("key-bkg-color");
  }
});

piano.addEventListener("mouseout", function (e) {
  e.target.classList.remove("key-bkg-color");
});

// Label Notes
keyAssist.addEventListener("click", function () {
  if (this.checked) {
    for (let i = 0; i < notes.length; ++i) {
      notes[i].style.fontSize = "1.8rem";
    }
  } else {
    for (let i = 0; i < notes.length; ++i) {
      notes[i].style.fontSize = "0";
    }
  }
});

// Menu Open Animation
let body = document.querySelector("body");
let menuBtn = document.getElementById("menu");
let isOpen = false;
menuBtn.addEventListener("click", function () {
  if (!isOpen) {
    body.style.left = "-30rem";
    isOpen = true;
  } else {
    body.style.left = "0";
    isOpen = false;
  }
});