Buildings disappear in high zoomlevel

Hi, I'm new in OSM mapping. I started to add some building arround my home. In the highest zoomlevel, the buildings disappear from the map. I have no idea, what I've done wrong. A cutout of the map can be found [here][1] [1]: http://hurlie.de/paul-ist-tot/images/13-03-16-a.png Tnx for your help, Andy