stop objects going through other objects

im making a brick game
i have 4 box collider(borders), capsule collider with rigidbody(paddle), and a sphere collider with rigidbody(ball). the sphere collider reflects off three of the box colliders but not the bottom box collider where the ball is destroyed. My paddle is the issue. If i hold down the arrow key to either side the paddle goes right through the box collider and shifts the paddle down a bit. I dont know how to keep the paddle inside the borders without it being forced out by just holding down the arrow key.

the setting on the paddle rigidbody is:
mass 1
drag 0
angular drag 0
unticked gravity
unticked kinematic
interpolate none
detection discrete
constraints frozen on Z pos
and all rotations

you can clamp the paddle manually.

transform.position = new Vector3(Mathf.Clamp(paddlePosition.x, minPosition, maxPosition), 0, 0);