what is wrong with this script

i have a third person character which uses rigid body. i want to change the height of the capsule collider as soon as my character jumps and return back the height capsule collider as soon as it is grounded. i am using curve in my animation to achieve this. but i don't understand what is wrong. my capsule collider height become zero as soon as i press jump. please note the collider height increases but become zero at end.

    {
    public float InputX;
     public float InputZ;
     public Vector3 desiredMoveDirection;
     public bool blockRotationPlayer;
     public float desiredRotationSpeed;


     public Animator anim;
     public float Speed;
     public float allowPlayerRotation;
     public Camera cam;
     public CharacterController controller;
     public bool isGrounded = false;
     private float verticalVel;
     private Vector3 moveVector;
     public float walkSpeed;
     public float runspeed;
     public bool Lshift;
     public bool Lcntrl;
     private bool jump = true;
     private Rigidbody rb;
     public float jumpDistance;
     public float jumpHeight;
     public float distToGround;
     public bool jumpUP = false ;
     public float time_to_down;
     
     
 
 
    
 
 
 
     // Use this for initialization
     void Start()
     {
         anim = this.GetComponent<Animator>();
         cam = Camera.main;
         rb = GetComponent<Rigidbody>();
         distToGround = GetComponent<Collider>().bounds.extents.y;
        
         
 
 
         
 
 
     }
 
     // Update is called once per frame
     void Update()
     {
         
         InputMagnitude();
                       
     }
 
     void PlayerMoveAndRotation()
     {
         InputX = Input.GetAxis("Horizontal");
         InputZ = Input.GetAxis("Vertical");
 
 
         var camera = Camera.main;
         var forward = cam.transform.forward;
         var right = cam.transform.right;
 
         forward.y = 0f;
         right.y = 0f;
 
         forward.Normalize();
         right.Normalize();
 
         desiredMoveDirection = forward * InputZ + right * InputX;
 
         if (blockRotationPlayer == false)
         {
             transform.rotation = Quaternion.Slerp(transform.rotation, Quaternion.LookRotation(desiredMoveDirection), desiredRotationSpeed);
 
         }
 
     }
 
     void InputMagnitude()
     {
         Lshift = Input.GetKey(KeyCode.LeftShift);
         
         
         //calculate input
         InputX = Input.GetAxis("Horizontal");
         InputZ = Input.GetAxis("Vertical");
 
 
         anim.SetFloat("InputZ", InputZ, 0.0f, Time.deltaTime * 2f);  //from animator float of InputX is called
         anim.SetFloat("InputX", InputX, 0.0f, Time.deltaTime * 2f); //from animator float of InputX is called
 
         //calculate the input magnitude
         Speed = new Vector2(InputX, InputZ).sqrMagnitude;
         // Grounded();
        
         IsGrounded();
         isJump(Speed);
         roll(Speed);
         
 
         if (Speed > allowPlayerRotation)
         {
             
             if ((Lshift) && (isGrounded))
             {
                 
                 anim.SetFloat("InputMagnitude", Speed * 1.0f, 0.5f, Time.deltaTime);
                 //transform.Translate(Vector3.forward * Speed * runspeed * Time.deltaTime);
                 rb.AddForce(transform.forward *Speed * runspeed, ForceMode.VelocityChange);
                 PlayerMoveAndRotation();
 
 
 
             }
             else if ((Lshift == false) && (isGrounded))
             {
              anim.SetFloat("InputMagnitude", Speed * 0.5f, 0.0f, Time.deltaTime);
      rb.AddForce(transform.forward * Speed * walkSpeed, ForceMode.VelocityChange);
                 PlayerMoveAndRotation();
                 
 
             }
 
 
 
 
         }
 
         else if (Speed < allowPlayerRotation)
         {
            
             anim.SetFloat("InputMagnitude", Speed, 0.0f, Time.deltaTime);
             
         }
     }
 
     void isJump(float Speed)
     {
         jump = Input.GetKey(KeyCode.Space);
         if (jump && isGrounded && Speed==0)
         {
             
             anim.SetBool("jumpUP", true);
             rb.AddForce(transform.up * jumpHeight, ForceMode.VelocityChange);
 
         }
             else
             {
                 anim.SetBool("jumpUP", false);
             }
         
         if (jump && Speed > 0 && isGrounded)
             {
             anim.SetBool("IsJump", true); 
             anim.SetFloat("jumDownSpeed", 0.3f);
             GetComponent<CapsuleCollider>().height = anim.GetFloat("jump_up_coll");
            
 
             rb.AddForce(transform.forward * jumpDistance, ForceMode.VelocityChange);
 
 
             Invoke ("jumpDown", time_to_down);
             }
             else
             {
                 anim.SetBool("IsJump", false);
         }
          }
 
 
        void IsGrounded()
     {
         if (!Physics.Raycast(transform.position, -Vector3.up, distToGround + 0.1f))
         {
             isGrounded = true;
             
         }
         else
         {
             isGrounded = false;
             
         }
     }
   
 
     void jumpDown()
     {
         anim.SetFloat("jumDownSpeed", 1.0f);
       //  GetComponent<CapsuleCollider>().height = anim.GetFloat("jump_down_coll");
     }
     void roll(float Speed)
     {
         Lcntrl = Input.GetKey(KeyCode.LeftControl);
         if (Speed>0 && isGrounded && Lcntrl)
         {
             anim.SetBool("StandRoll", true);
         }
         else
         {
             anim.SetBool("StandRoll", false);
         }
     }
     
 }