Also, it seems your js is also contributing to the issue. I have found a temporary fix, but you should really fix this as it would be easy to do.
For anybody else with this issue, this is how I’m fixing it for now:
function my_admin_enqueue($hook) {
if ( 'post.php' != $hook ) {
return;
}
wp_dequeue_style( 'wpl_backend_main_style' );
wp_dequeue_script( 'wpl_backend_javascript' );
}
add_action( 'admin_enqueue_scripts', 'my_admin_enqueue' );