Bug-fixing. Endless running in my game after hitting a collider and moving again against it

hey guys, so I have set up an alpha version of my WIP game to let my friends test it for bugs. They found out that there is something wrong with my collision script. When they move the character to another collider (e.g. fence) and press the button multiple times fast in a row, the character is starting to run again. against the fence but you cannot move it anymore. I hope you guys can help me. I post the link to my game as well as the code.
Game: http://nubz.parseapp.com/

charMovement script:

Code (CSharp):

1.     void FixedUpdate ()
2.     {
3.  
4.         if (Input.GetKeyDown (KeyCode.LeftArrow) && rigidbody.isKinematic == true){
5.             rigidbody.isKinematic = false;
6.             rigidbody.velocity = new Vector3(0, 0, speed);
7.             transform.rotation = Quaternion.LookRotation(rigidbody.velocity);
8.             anim.speed = animSpeed;  
9.             anim.SetFloat("Speed", animSpeed);
10.            
11.         }
12.         if (Input.GetKeyDown (KeyCode.RightArrow) && rigidbody.isKinematic == true){
13.             rigidbody.isKinematic = false;
14.             rigidbody.velocity = new Vector3(0, 0, -speed);
15.             transform.rotation = Quaternion.LookRotation(rigidbody.velocity);
16.             anim.speed = animSpeed;  
17.             anim.SetFloat("Speed", animSpeed);
18.            
19.            
20.         }
21.         if (Input.GetKeyDown (KeyCode.UpArrow) && rigidbody.isKinematic == true){
22.             rigidbody.isKinematic = false;
23.             rigidbody.velocity = new Vector3(speed, 0, 0);
24.             transform.rotation = Quaternion.LookRotation(rigidbody.velocity);
25.             anim.speed = animSpeed;  
26.             anim.SetFloat("Speed", animSpeed);
27.            
28.            
29.         }
30.         if (Input.GetKeyDown (KeyCode.DownArrow) && rigidbody.isKinematic == true){
31.             rigidbody.isKinematic = false;
32.             rigidbody.velocity = new Vector3(-speed, 0, 0);
33.             transform.rotation = Quaternion.LookRotation(rigidbody.velocity);
34.             anim.speed = animSpeed;  
35.             anim.SetFloat("Speed", animSpeed);
36.         }
37.        
38.        
39.  
40.     }

collision script that is attached to every object at the field:

Code (CSharp):

1.     private Animator anim;
2.  
3.     void OnCollisionEnter ( Collision collision) {
4.         if (collision.gameObject.CompareTag ("Player")) {
5.             anim = collision.gameObject.GetComponent<Animator>();
6.             anim.SetFloat("Speed", 0);
7.             collision.rigidbody.isKinematic = true;
8.             }
9.         }
10.     void OnCollisionExit ( Collision collision) {
11.         collision.rigidbody.isKinematic = true;
12.         }

 

Sometimes collisions don't register if the collision happens really fast. You could check if they still haven't left the collision by checking void OnCollisionStay(Collision coll) {}

http://docs.unity3d.com/ScriptReference/MonoBehaviour.OnCollisionStay.html