gmaps ng-maps custom marker moving on zooming in/out

Question

I have created a custom marker with the html documentation from ng-maps as below:

<custom-marker position="{{listCtrl.searchPoint.lat}},{{listCtrl.searchPoint.lng}}">
    <div class="bu-map__marker">
        <span class="icon ion-location"></span>
    </div>
</custom-marker>

The position are simple coordinates however when I zoom out the position of the marker moves off the position of the coordinates.

There is not any particular css on the marker, it is just an icon.

I know there are a few options in terms of anchor, origin, scaleSize when using google maps javascript markers api however can these be used with the ng-maps custom markers?

Sachin