Uncaught TypeError: $(…).ajaxError is not a function

Oh @wfgerald, i see. The problem is, that i use the latest jQuery version (3.4.1), not that wp built-in from several years old ver. 1.2 branch. Interesting, you are the only plugin, that got problems with that.
P.S: this is my setup if you want to test it with modern jquery

//Remove JQuery migrate
function remove_jquery_migrate($scripts)
{
    if (!is_admin() && isset($scripts->registered['jquery'])) {
        $script = $scripts->registered['jquery'];
        
        if ($script->deps) { // Check whether the script has any dependencies
            $script->deps = array_diff($script->deps, array(
                'jquery-migrate'
            ));
        }
    }
}

add_action('wp_default_scripts', 'remove_jquery_migrate');

//Making jQuery to load from Google Library
function replace_jquery() {
	if (!is_admin()) {
		// comment out the next two lines to load the local copy of jQuery
		wp_deregister_script('jquery');
		wp_register_script('jquery', '//code.jquery.com/jquery-3.4.1.slim.min.js', false, NULL,true);
		wp_enqueue_script('jquery');                                                                           
        wp_script_add_data( 'jquery', 'integrity', 'sha256-pasqAKBDmFT4eHoN2ndd6lN370kFiGUFyTiUHWhU7k8=');
        wp_script_add_data( 'jquery', 'crossorigin', 'anonymous' );
	}    
}
add_action('init', 'replace_jquery');