Weird collision/physics problem. HELP,Weird physics/collision problem

So i have a rotating circle with an opening at some point. In circle there are sphere objects which fall out when the opening is reached. Spheres are prefabs with rigidbody and sphere colliders, if i have only 1 of these spheres everything works fine, but if i have 2 or more they get stuck together and physics doesn't work on them, they're frozen on one place. If i move one of them by hand it magically starts working again. help? There are no scripts attached to balls.