Why are clusters on Google Maps not clickable?

Question

JavaScript

Greetings.
I display a Google map, clusters are displayed, but when hovering over a cluster, it is not clickable. Instead, "movement" continues to be displayed. Example:

It is also not clear why the blocks are stretched on the left and there are no inscriptions on the buttons in the lower right corner.
The code:

function initialize() {
    var mapOptions = {
        center: new google.maps.LatLng(39, -95),
        zoom: 3,
        mapTypeId: google.maps.MapTypeId.ROADMAP
    }
    var map = new google.maps.Map(document.getElementById('map_canvas'), mapOptions);

    var markers = [];
    for (var i = 0; i < locations.length; i++) {
        var marker = new google.maps.Marker({
            position: new google.maps.LatLng(locations[i][2], locations[i][3]),
            url: locations[i][1],
            title: locations[i][0]
        });
        google.maps.event.addListener(marker, 'click', function() {
            window.location.href = this.url;
        });
        markers.push(marker);
    }
    var markerCluster = new MarkerClusterer(map, markers);
}
google.maps.event.addDomListener(window, 'load', initialize);

Has anyone encountered a problem?