My problem is that both SiteA and SiteB controls appear on the same location!
I've also tried to directly copy and paste the xaml from the online example, but the result is exactly the same! All the ElementLayer children appear on the same location (somewhere in the middle of the screen - see attachment).
Your basemap uses a web Mercator spatial reference, so your map uses the same SR and you have to set the coordinates of your elements in these coordinates (instead of geographical coordinates). You can use the WebMercator class to transform your WGS84 coordinates to web Mercator.