Well, they just had some space left and dumped a piece of art (heap of metal) on it ;)
I found a link which explains it all: http://www.dse.nl/~hanevoet/fotoosarieb/arieb.html
Mine does the same when it's cold. If I heat it up for a couple of minutes (with body heat of course, don't put it on the central heating ;)) it works fine and stays very stable.