Custom post type order by post_title

I found the solution. When I take my first query and make it like this:

<?php
return [
  "post_type" => [
    "employees"
  ],
  "post_status" => [
    "publish"
  ],
  "orderby" => [
   "post_title" => "ASC"
],
  "posts_per_page" => "99"
];

the sorting is working. So I replaced:

"orderby" => [
"post_title"
],
"order" => [
"ASC"
],

with only:

"orderby" => [
"post_title" => "ASC"
],

This did the trick:)