Custom Walker Menu – Depth Issue

I am looking at a site that uses a custom walker menu. The submenu works but a 2nd level submenu does not. I’m not sure if this is an issue with the walker script or with the css.

The walker script is

<br />
//Custom Menu Walker<br />
class Custom_Walker_Nav_Menu extends Walker_Nav_Menu {<br />
	function start_lvl(&$output, $depth) {<br />
		$indent = str_repeat("\t", $depth);<br />
		$output .= "\n$indent<div class='drop'>
<ul>\n";<br />
	}</p>
<p>	function end_lvl(&$output, $depth) {<br />
		$indent = str_repeat("\t", $depth);<br />
		$output .= "$indent</ul>
</div>\n";<br />
	}</p>
<p>	function start_el(&$output, $item, $depth, $args) {<br />
		global $wp_query;<br />
		$indent = ( $depth ) ? str_repeat( "\t", $depth ) : '';</p>
<p>		$class_names = $value = '';</p>
<p>		$classes = empty( $item->classes ) ? array() : (array) $item->classes;<br />
		$classes[] = 'menu-item-' . $item->ID;</p>
<p>		$class_names = join( ' ', apply_filters( 'nav_menu_css_class', array_filter( $classes ), $item, $args ) );<br />
		$class_names = ' class="' . esc_attr( $class_names ) . '"';</p>
<p>		$id = apply_filters( 'nav_menu_item_id', 'menu-item-'. $item->ID, $item, $args );<br />
		$id = strlen( $id ) ? ' id="' . esc_attr( $id ) . '"' : '';</p>
<p>		$output .= $indent . '<li' . $id . $value . $class_names .'>';</p>
<p>		$attributes  = ! empty( $item->attr_title ) ? ' title="'  . esc_attr( $item->attr_title ) .'"' : '';<br />
		$attributes .= ! empty( $item->target )     ? ' target="' . esc_attr( $item->target     ) .'"' : '';<br />
		$attributes .= ! empty( $item->xfn )        ? ' rel="'    . esc_attr( $item->xfn        ) .'"' : '';<br />
		$attributes .= ! empty( $item->url )        ? ' href="'   . esc_attr( $item->url        ) .'"' : '';</p>
<p>		$item_output = $args->before;<br />
		if(strpos($class_names, 'notlink')){<br />
			$item_output .= '<span class="link">';<br />
			$item_output .= $args->link_before . apply_filters( 'the_title', $item->title, $item->ID ) . $args->link_after;<br />
			$item_output .= '</span>';<br />
		}else{<br />
			$item_output .= '<a'. $attributes .'>';<br />
			$item_output .= $args->link_before . apply_filters( 'the_title', $item->title, $item->ID ) . $args->link_after;<br />
			$item_output .= '';<br />
		}</p>
<p>		$item_output .= $args->after;</p>
<p>		$output .= apply_filters( 'walker_nav_menu_start_el', $item_output, $item, $depth, $args );<br />
	}</p>
<p>	function end_el(&$output, $item, $depth) {<br />
		$output .= "\n";<br />
	}<br />
}<br />

and it’s being called via

wp_nav_menu (array('container' => false,
'theme_location' => 'primary',
'menu_id' => '',
'menu_class' => 'navigation',
'items_wrap' => '<ul id="%1$s" class="%2$s">%3$s',
'walker' => new Custom_Walker_Nav_Menu)
);

The site is

https://cmcb.org

Thanks,