Invisible Armorstands disappear on death

I'm using invisible armostands with blocks on their hads to create a "level-choosing-system". The amorstands are rotating via a clock using /entitydata.
I killed myself and the armorstands disappeard. It is kind of random because it happens not everytime, but i think about 33% of it.
Even in gamemode 3 the amorstands disappeard. Reloading chunks with F3+A did not help. After relogging they were back. They are within the spawchunks.