Problem with Collision and NavMeshAgent

I have enemies with NavMeshAgents attached.

I want the enemies to collide with one another, and so I have rigidbodies attached. This works. However, they will not go over slopes with rigidbodies attached, but will if I make them kinematic or disable the rigidbodies altogether, but this causes them to intersect each other. Any ideas?

You could try adding a lifter sphere to let them step over small obstacles.