Coroutine called more than once

Hello all and good day!

I am new to unity and I am creating a game based on grid system. I want to move the player's unit from one grid to another based on their input from joystick. However, I am getting strange behavior of:

- unit moving less than it should be (if player move joystick four times there should be four moves)
- sometimes a movement is much slower than it should be (given the speed I set)
- from the log I see that sometimes it only record one joystick input but multiple times of movement.

I am suspecting somewhere in the code I let the coroutine to call more than once, which is not what I intend. I understand that there are similar questions that have been asked but I still couldn't get a clue on what is wrong with my code. So, I would like to obtain some advice from you guys on which direction should I check. Appreciate your time reading this and sorry for my bad English.

Thank you and have a great day!

Here are extract of my code:

 public class GameHandler : MonoBehaviour
 {
     //To get player input from joystick
     void Update()
     {
         float verticalDirection = variableJoystick.Vertical;
         float horizontalDirection = variableJoystick.Horizontal;
         if (!inAction)
         {
             inAction = true;
 
             // Joystick Up
             if (verticalDirection > 0.5 && Mathf.Abs(horizontalDirection) < 0.5)
             {
                 StartCoroutine(PlayerMove(PlayerUnit.MoveDirection.Up));
                 Debug.Log("joystick moved");
             }
 
             // Joystick Down
             else if (verticalDirection < -0.5 && Mathf.Abs(horizontalDirection) < 0.5)
             {
                 StartCoroutine(PlayerMove(PlayerUnit.MoveDirection.Down));
                 Debug.Log("joystick moved");
             }
 
             // Joystick Right
             else if (horizontalDirection > 0.5 && Mathf.Abs(verticalDirection) < 0.5)
             {
                 StartCoroutine(PlayerMove(PlayerUnit.MoveDirection.Right));
                 Debug.Log("joystick moved");
             }
 
             // Joystick Left
             else if (horizontalDirection < -0.5 && Mathf.Abs(verticalDirection) < 0.5)
             {
                 StartCoroutine(PlayerMove(PlayerUnit.MoveDirection.Left));
                 Debug.Log("joystick moved");
             }
 
             else
             {
                 inAction = false;
                 //Debug.Log("joystick moved a little");
             }
         }
     }
 
     //Player's move
     IEnumerator PlayerMove(BattleUnit.MoveDirection moveDirection)
     {
         Debug.Log("Player Move");
 
         battleUnit.UnitMove(moveDirection);
 
         while (canProceed == false)
         {
             yield return null;
         }
 
         if (activePlayerUnit.actionPoint <= 0)
         {
             EndThisTurn();
         }
 
         inAction = false; //Completed action
         canProceed = false; // Set up for next action
     }
 }
 
 
 public class BattleUnit : MonoBehaviour
 {
     // Find movement destination
     public void UnitMove(MoveDirection moveDirection)
     {
         Map map = GameObject.Find("GridMapManager").GetComponent<Map>();
         BattleGrid targetGrid = null;
 
         switch (moveDirection)
         {
             case MoveDirection.Up:
                 targetGrid = map.GetGridObject(belongGrid.GetX(), belongGrid.GetY() + 1);
                 //belongGrid.GetX
                 break;
             case MoveDirection.Down:
                 targetGrid = map.GetGridObject(belongGrid.GetX(), belongGrid.GetY() - 1);
                 break;
             case MoveDirection.Left:
                 targetGrid = map.GetGridObject(belongGrid.GetX() - 1, belongGrid.GetY());
                 break;
             case MoveDirection.Right:
                 targetGrid = map.GetGridObject(belongGrid.GetX() + 1, belongGrid.GetY());
                 break;
         }
 
         StartCoroutine(UnitMoveCoroutine(targetGrid));
     }
 
     // Move player's unit to destination
     IEnumerator UnitMoveCoroutine(BattleGrid targetGrid)
     {
         GameHandler gameHandler = GameObject.Find("GameHandler").GetComponent<GameHandler>();
         Map map = GameObject.Find("GridMapManager").GetComponent<Map>();
 
         float speed = 2.8f;
         float step = speed * Time.deltaTime;
         moveDone = false;
 
         if (targetGrid == null || targetGrid.isOccupied == true)
         {
             Debug.Log("cannot move to target");
             moveDone = true;
         }
         else
         {
             while (moveDone == false)
             {
                 transform.position = Vector3.MoveTowards(transform.position, map.GetWorldPosition(targetGrid), step);
 
                 if (transform.position == map.GetWorldPosition(targetGrid))
                 {
                     Debug.Log("Unit Arrived!");
                     actionPoint -= targetGrid.actionPointUse;
                     gameHandler.canProceed = true; // Indicate player action finished and can proceed to next action
                     moveDone = true;
                 }
                 yield return null;
             }
         }
     }
 }