Conecting snake parts

Hi, I'm making snake and i have an problem with part conection. Each part has an script with own smooth grid movement:

 using UnityEngine;
 using System.Collections;
 
 public enum Direction { Right, Up, Left, Down}
 
 public class Part : MonoBehaviour 
 {
     public const float speed = 0.5f;
     public Direction direction = Direction.Right;
     public Vector3 endpos;                                  //target coordinates
     public bool isMoving = false;                           //serves to indicate if the part is on the center of cell
     
     public bool changedDirection = false;                   //serve to indicate if direction is changed
     public int partRank;                                    //register order of the part
     public Vector3 ChangingPosition;                        //this is a position where parts should change their direction  
 
     void Update()
     {
         if (isMoving == false)
         {
             endpos = transform.position;
 
             if (direction == Direction.Right)
             {
                 endpos += Vector3.right;
             }
             else if (direction == Direction.Up)
             {
                 endpos += Vector3.up;
             }
             else if (direction == Direction.Left)
             {
                 endpos += Vector3.left;
             }
             else if (direction == Direction.Down)
             {
                 endpos += Vector3.down;
             }
 
             isMoving = true;
         }
 
         if (isMoving == true)
         {
             transform.position = Vector3.MoveTowards(transform.position, endpos, speed * Time.deltaTime);
             if (transform.position == endpos)
             {
                 isMoving = false;
 
                 if (changedDirection == true && transform.position == ChangingPosition)
                 {
                     GameObject g = gameObject.GetComponentInParent<Snake>().snakeParts[partRank] as GameObject;
                     //g.GetComponent<Part>().direction = direction;
                     StartCoroutine("setDirection", g);
                     g.GetComponent<Part>().changedDirection = true;
                     g.GetComponent<Part>().ChangingPosition = ChangingPosition;
                     changedDirection = false;
                 }
             }
         }
     }
 
     IEnumerator setDirection(GameObject g)
     {
         yield return new WaitForSeconds(Time.deltaTime);
         g.GetComponent<Part>().direction = direction;
     }
 }

Parts transmit informations about changing their direction. It works, but if i change direction twice consecutively it doesn't work.

To all parts is superior one object, which changes direction with following script: using UnityEngine; using System.Collections;

 public class Snake : MonoBehaviour 
 {
     public GameObject hlava;
     public GameObject clanek;
     public GameObject ocas;
 
     public ArrayList snakeParts = new ArrayList();
 
     void Start()
     {
         GameObject head = Instantiate(this.hlava, new Vector3(0, 0, 0), new Quaternion(0, 0, -90, 90)) as GameObject;
         this.snakeParts.Add(head);
         head.GetComponent<Part>().partRank = 1;
         head.transform.parent = transform;
         GameObject part1 = Instantiate(this.clanek, new Vector3(-1, 0, 0), new Quaternion(0, 0, -90, 90)) as GameObject;
         this.snakeParts.Add(part1);
         part1.GetComponent<Part>().partRank = 2;
         part1.transform.parent = transform;
         GameObject part2 = Instantiate(this.clanek, new Vector3(-2, 0, 0), new Quaternion(0, 0, -90, 90)) as GameObject;
         this.snakeParts.Add(part2);
         part2.GetComponent<Part>().partRank = 3;
         part2.transform.parent = transform;
         GameObject part3 = Instantiate(this.clanek, new Vector3(-3, 0, 0), new Quaternion(0, 0, -90, 90)) as GameObject;
         this.snakeParts.Add(part3);
         part3.GetComponent<Part>().partRank = 4;
         part3.transform.parent = transform;
         GameObject tail = Instantiate(this.ocas, new Vector3(-4, 0, 0), new Quaternion(0, 0, -90, 90)) as GameObject;
         this.snakeParts.Add(tail);
         tail.GetComponent<Part>().partRank = 5;
         tail.transform.parent = transform;
     }
 
     void Update()
     {
         if (Input.GetKey(KeyCode.RightArrow))
         {
             GameObject g = snakeParts[0] as GameObject;
             g.GetComponent<Part>().direction = Direction.Right;
             g.GetComponent<Part>().changedDirection = true;
             g.GetComponent<Part>().ChangingPosition = g.GetComponent<Part>().endpos;
         }
         else if (Input.GetKey(KeyCode.UpArrow))
         {
             GameObject g = snakeParts[0] as GameObject;
             g.GetComponent<Part>().direction = Direction.Up;
             g.GetComponent<Part>().changedDirection = true;
             g.GetComponent<Part>().ChangingPosition = g.GetComponent<Part>().endpos;
         }
         else if (Input.GetKey(KeyCode.DownArrow))
         {
             GameObject g = snakeParts[0] as GameObject;
             g.GetComponent<Part>().direction = Direction.Down;
             g.GetComponent<Part>().changedDirection = true;
             g.GetComponent<Part>().ChangingPosition = g.GetComponent<Part>().endpos;
         }
         else if (Input.GetKey(KeyCode.LeftArrow))
         {
             GameObject g = snakeParts[0] as GameObject;
             g.GetComponent<Part>().direction = Direction.Left;
             g.GetComponent<Part>().changedDirection = true;
             g.GetComponent<Part>().ChangingPosition = g.GetComponent<Part>().endpos;
         }
     }
 }

Does anyone have any advice? Maybe there is a better solution, than delay by coroutine.