WooCommerce minicart custom quantity buttons throwing an Internal error 500 on wp_admin-ajax.php

I am looking for some help with this as I cant seem to figure it out.
I want to add quantity selector buttons to the mini cart without using a paid plugin, I thought it would be "fairly simple"

This is the code I added to mini-cart.php ( Elementor Menu cart widget (pro) )

<div class="quantity-buttons">
<button class="decrement-quantity" data-product-id="<?php echo esc_attr( $product_id ); ?>" data-cart-item-key="<?php echo esc_attr( $cart_item_key ); ?>">-</button>
<input type="number" class="quantity-input" value="<?php echo esc_attr( $cart_item['quantity'] ); ?>" min="1" max="100" data-product-id="<?php echo esc_attr( $product_id ); ?>" data-cart-item-key="<?php echo esc_attr( $cart_item_key ); ?>">
<button class="increment-quantity" data-product-id="<?php echo esc_attr( $product_id ); ?>" data-cart-item-key="<?php echo esc_attr( $cart_item_key ); ?>">+</button>
</div>

This is the jquery I used to update the quantity onChange. Added in codesnippets with 1 priority

<script>
jQuery(document).ready(function($) {
$('.quantity-buttons').on('click', '.decrement-quantity, .increment-quantity', function(e) {
e.preventDefault();
var button = $(this);
var productId = button.data('product-id');
var cartItemKey = button.data('cart-item-key');
var quantityInput = button.siblings('.quantity-input');
var quantity = parseInt(quantityInput.val());
var newQuantity = quantity;
if (button.hasClass('decrement-quantity')) {
newQuantity = quantity - 1;
} else if (button.hasClass('increment-quantity')) {
newQuantity = quantity + 1;
}
if (newQuantity < 1 || isNaN(newQuantity)) {
newQuantity = 1;
}
quantityInput.val(newQuantity);
// AJAX request to update the quantity
$.ajax({
url: '<?php echo esc_url( wc_ajax_url() ); ?>',
type: 'POST',
data: {
action: 'update_mini_cart_quantity',
product_id: productId,
cart_item_key: cartItemKey,
quantity: newQuantity
},
success: function(response) {
// Update mini cart contents
if (response && response.fragments) {
$.each(response.fragments, function(key, value) {
$(key).replaceWith(value);
});
}
}
});
});
});
</script>

And lastly, this was added to function.php

add_action('wp_ajax_update_mini_cart_quantity', 'update_mini_cart_quantity');
add_action('wp_ajax_nopriv_update_mini_cart_quantity', 'update_mini_cart_quantity');
function update_mini_cart_quantity() {
if (isset($_POST['product_id']) && isset($_POST['cart_item_key']) && isset($_POST['quantity'])) {
$product_id = sanitize_text_field($_POST['product_id']);
$cart_item_key = sanitize_text_field($_POST['cart_item_key']);
$quantity = intval($_POST['quantity']);
if ($quantity < 1) {
$quantity = 1;
}
// Update the quantity in the cart
WC()->cart->set_quantity($cart_item_key, $quantity, true);
// Calculate cart totals
WC()->cart->calculate_totals();
// Prepare cart fragments for AJAX response
$cart_fragments = WC()->cart->get_refreshed_fragments();
// Return updated fragments as JSON response
wp_send_json_success($cart_fragments);
}
wp_send_json_error();
}

What am I doing wrong? Should I provide the URL for the live site?

I expanded the memory limit as suggested by most people, but that didnt help.
I tried resetting the plugins one by one to see if there was any collisions, that didnt help.

On WordPress Ajax PHP function hooked inwp_ajax_{$action} and/or wp_ajax_nopriv_{$action} hooks, die(); or wp_die(); is always required, at the end of the code before the last closing }, to stop execution afterward, avoiding an Internal Error 500 on wp_admin-ajax.php…

add_action('wp_ajax_my_action', 'get_my_action');
add_action('wp_ajax_nopriv_my_action', 'get_my_action');
function get_my_action() {
// Here come your code
wp_die(); // Always at the end to stop execution afterward
}

See official WordPress code example