Ball bounces at different heights when it shouldn't

I have a simple game where i have a ball that falls onto a square. I have code set up that makes it so that the ball can only bounce when it is touching the cube and when i press any button. I want the ball to jump at the same height every time i press the button but it won't. Most of the time it jumps the same height but on some occasions, the ball will either bounce higher. Here is code:

 void OnCollisionEnter2D(Collision2D col) {
         if (col.gameObject.tag == "Death") {
             Debug.Log ("You have succeeded");
             canJump = true;
         }
     }
 
     void OnCollisionExit2D (Collision2D col) {
         if (col.gameObject.tag == "Death") {
             canJump = false;
             circle.GetComponent <PlanetRotation> ().rotateSpeed = 0;
         }
     }
         
     void Update () {
         if (canJump == true) {
             if (Input.anyKey) {
                 rb.AddForce (Vector2.up * jumpHeight);
             }
         }
     }
     public void AdjustJumpHeight(float newJumpHight) {
         jumpHeight = newJumpHight;
     }
 }