Yeah I have a fix, just haven’t had time to include it in the next version. You can however open the /js/nwm-gmap3.js. Then look for the imageLoader function on line 467.
Replace the code in the function with this, that should fix it.
var $li = $map.find( ".nwm-active-destination" ),
img = new Image(),
imgTarget = $li.find( ".nwm-thumb" ),
imgSrc = $li.find( ".nwm-thumb" ).data( "src" ),
id = $li.data( "id" ),
preloader = '<img class="nwm-preloader" id="nwm-preload-img-' + id + '" src="' + nwmSettings.path + 'admin/img/ajax-loader.gif" />';
if ( $.inArray( id, loadedImageList ) === -1 ) {
$li.append( preloader );
img.onload = function(){
$( "#nwm-preload-img-" + id ).remove();
imgTarget.attr( "src", this.src );
loadedImageList.push( id );
};
img.src = imgSrc;
} else {
imgTarget.attr( "src", imgSrc );
}