From wp-admin > Plugins > Add New > Search "enable Jquery Migrate Helper"
Install and activate
Then add this code in your wplms customizer plugin
add_action( 'admin_enqueue_scripts', 'enqueue_jquery_for_select2');
function enqueue_jquery_for_select2(){
wp_enqueue_style('select2', 'https://cdnjs.cloudflare.com/ajax/libs/select2/4.0.3/css/select2.min.css' );
wp_enqueue_script('select2', 'https://cdnjs.cloudflare.com/ajax/libs/select2/4.0.3/js/select2.min.js', array('jquery') );
}
Then check again