Syntax error, unrecognized expression for href

you may add the below code in functions.php

function modify_jquery() {
if (!is_admin()) {
	wp_deregister_script('jquery');
	wp_register_script('jquery', 'https://code.jquery.com/jquery-1.11.3.min.js');
	wp_enqueue_script('jquery');
}
}
add_action('init', 'modify_jquery');

I tried the solution provided by

https://github.com/jquery/jquery/issues/2885

which worked for me. I search for [href=#] in js and replace with [href*=\\#]

a[href*=\\#]:not([href=\\#])

You need to enclose special characters in quotes when using a attribute based selector.

if ($('ul li a[href="' + id + '"]').length) {

Your version of selector would result

if ($("ul li a[href=#!...]").length) {

The #! will throw unrecognized expression.

My version where the "" escape the characters

if ($('ul li a[href="#!..."]').length) {