Collision Not Working

My player a rigid body controlled using Input is not colliding with an enemy when no keys are pressed. When no keys are pressed enemy simply goes through the player without collision.

The OnCollisionEnter methods only gets called when I’m pressing a key in keyboard:

void OnCollisionEnter(Collision other)
	if (other.collider.tag == "enemy") {
		Die ();

Player Collision Settings:alt text

Enemy Collision Settings: alt text

Move EVERY RIGIDBODY that needs to be moved in FixedUpdate. Use either MovePosition on kinematic Rigidbodies, or change their velocity if not. Any other way bypasses the physics engine.