It seem that the problem is not the number of entitys. If I use Spheres everything works fine but when I try to use boxes (for a destroyable brick construction) the problem happens again. The boxes are not extactly one on an other. (can not explain in english and do it in german: Die einzelnen Steine verschmelzen ein kleines Stück (rutschen ineinander) - if anybody can translate it - please do it)