Sphere vs Capsule collider collision resolution

When moving a sphere collider rigidbody around with AddForce(), it seems to respond to other colliders accurately. It can hit solid objects and push up against them flush with continued force. Using the same code on a capsule collider of similar size, it penetrates other colliders and rebounds, but only on a flat side. Both objects have zero friction and bounce, as do the environment colliders.

Any ideas as to why these would behave differently? Am I seeing some artifact of capsule collider optimization?