Marble refuses to jump sometimes

I have a marble rolling game controlled by UI buttons for mobile. I'm using the SendMessage system to have the buttons talk to the Player Movement script. The jumping works most of the time, but sometimes randomly it would refuse to jump, thus really messing up the experience. Also, sometimes when it refuses to jump, it would apply 2x the force when I jump again making the marble jump 2x higher. I tried a cooldown script to prevent this 2x force. I think it reduced the amount of 2x jump, but it still happens.

I've been trying to fix this for days to no avail. Here's my code:

 using UnityEngine;
 using System.Collections;
 
 public class PlayerMovement : MonoBehaviour {
     public float spinTorque;
     public float airSpeed;
     public float MaxAngularVelocity;
     private Vector3 Jump;
     public float JumpStrength = 1000;
     public GameObject Camera;
     public AudioSource CollisionSound;
     public float RollDrag = 1;
     public AudioSource JumpSound;
     public AudioSource RollSound;
     public AudioSource BounceSound;
     public CNAbstractController MovementJoystick;
     private bool inAir = true;
     private bool isJumping = false;
     private Vector3 NormalDirection;
 
     // Use this for initialization
     void Start () {
         inAir = true;
         RollSound.Play ();
         GetComponent<Rigidbody>().maxAngularVelocity = MaxAngularVelocity;
     }
 
     void FixedUpdate () {
         print (inAir);
         //Ball air and spin movement.
         //Airspeed
         float hf = MovementJoystick.GetAxis ("Horizontal") * airSpeed * Time.deltaTime; //Touch Joystick Input
         float vf = MovementJoystick.GetAxis ("Vertical") * airSpeed * Time.deltaTime;
         float jhf = Input.GetAxis ("Horizontal") * airSpeed * Time.deltaTime; //Keyboard/Joystick Input
         float jvf = Input.GetAxis ("Vertical") * airSpeed * Time.deltaTime;
     
         float h = MovementJoystick.GetAxis ("Horizontal") * spinTorque * Time.deltaTime; //Touch Joystick Input
         float v = MovementJoystick.GetAxis ("Vertical") * spinTorque * Time.deltaTime;
         float jh =  Input.GetAxis ("Horizontal") * spinTorque * Time.deltaTime; //Keyboard/Joystick Input
         float jv =  Input.GetAxis ("Vertical") * spinTorque * Time.deltaTime;
         if (inAir == true) {
     
             GetComponent<Rigidbody> ().AddForce (Camera.transform.right * hf);
             GetComponent<Rigidbody> ().AddForce (Camera.transform.forward * vf);
             GetComponent<Rigidbody> ().AddForce (Camera.transform.right * jhf);
             GetComponent<Rigidbody> ().AddForce (Camera.transform.forward * jvf);
         }
         GetComponent<Rigidbody> ().AddTorque (Camera.transform.forward * -h);
         GetComponent<Rigidbody> ().AddTorque (Camera.transform.right * v);
         GetComponent<Rigidbody> ().AddTorque (Camera.transform.forward * -jh);
         GetComponent<Rigidbody> ().AddTorque (Camera.transform.right * jv);
             
             
     }
 
     void Update () {
         // Sound pitch control
         if (inAir == false) {
             RollSound.volume = GetComponent<Rigidbody> ().velocity.magnitude / 15;
             RollSound.pitch = GetComponent<Rigidbody> ().velocity.magnitude / 25 + 0.3f;
             RollSound.pitch = Mathf.Clamp (RollSound.pitch, 0.1f, 1f);
         } else {
             RollSound.volume = 0;
         }
     }
     void OnCollisionStay (Collision collision) {
         //Jump effects.
         NormalDirection = collision.contacts [0].normal;
         if (isJumping == true) {
             StartCoroutine(JumpCooldown());
         }
 
     }
     void OnCollisionEnter (Collision collision){
         CollisionSound.volume = collision.relativeVelocity.magnitude/100;
         CollisionSound.Play ();
         inAir = false;
         GetComponent<Rigidbody> ().drag = RollDrag;
     }
     void OnCollisionExit (){
         inAir = true;
         GetComponent<Rigidbody> ().drag = 0;
     }
 
     void JumpActive (){
         StopCoroutine (Jumping ());
         StartCoroutine (Jumping ());
 
 
     }
 
     IEnumerator Jumping (){
         isJumping = true;
         yield return new WaitForSeconds (0.01f);
         isJumping = false;
     }
     IEnumerator JumpCooldown(){
         GetComponent<Rigidbody>().AddForce(NormalDirection * JumpStrength);
         JumpSound.Play ();
         yield return new WaitForSeconds (0.05f);
     }
 }