Unity Animation.CrossFade Animation.Play

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class PlayerControll : MonoBehaviour
{
    Transform playerTransform;
    Animation playerAnimation;
    Rigidbody playerRigidbody;
    public float moveSpeed;
    public float jumpAbility;
    bool canJump;

    void Start()
    {
        playerTransform = GetComponent<Transform>();
        playerAnimation = GetComponent<Animation>();
        playerRigidbody = GetComponent<Rigidbody>();
        Debug.Log(playerTransform.name);
    }

    void Update()
    {
        Move_Control();
    }

    void Move_Control()
    {
        if (Input.GetKey(KeyCode.W))
        {
            playerTransform.Translate(Vector3.forward * Time.deltaTime * moveSpeed, Space.Self);
            playerAnimation.Play("runforward");
        }

        if (Input.GetKeyUp(KeyCode.W))
        {
            playerAnimation.CrossFade("idle", 0.3f);
        }

        if (Input.GetKey(KeyCode.S))
        {
            playerTransform.Translate(Vector3.back * Time.deltaTime * moveSpeed, Space.Self);
            playerAnimation.Play("runbackwards");
        }
        if (Input.GetKeyUp(KeyCode.S))
        {
            playerAnimation.CrossFade("idle", 0.3f);
        }

        if (Input.GetKey(KeyCode.A))
        {
            playerTransform.Translate(Vector3.left * Time.deltaTime * moveSpeed, Space.Self);
            playerAnimation.Play("strafeleft");
        }

        if (Input.GetKeyUp(KeyCode.A))
        {
            playerAnimation.CrossFade("idle", 0.3f);
        }

        if (Input.GetKey(KeyCode.D))
        {
            playerTransform.Translate(Vector3.right * Time.deltaTime * moveSpeed, Space.Self);
            playerAnimation.Play("straferight");
        }

        if (Input.GetKeyUp(KeyCode.D))
        {
            playerAnimation.CrossFade("idle", 0.3f);
        }

        if (Input.GetKey(KeyCode.Space))
        {
            if (canJump)
            {
                playerRigidbody.AddForce(Vector3.up * jumpAbility, ForceMode.Impulse);
                playerAnimation.Play("jump");
                canJump = false;
            }
        }
    }

    private void OnCollisionStay(Collision collision)
    {
        if (collision.transform.tag == "Ground")
        {
            canJump = true;
            //playerAnimation.Play("idle");
            playerAnimation.CrossFade("idle",0.2f);
        }
    }
}

按88行那樣寫只摁WSAD中的一個按鍵人物正常移動，但是不正常執行動畫，人物會漂移；按89行那樣寫只摁WSAD中的一個按鍵人物正常移動，並且正常執行動畫。

但是同時摁下WD或WA或SD或SA，人物都會漂移。