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行那样写只摁WSAD中的一个按键人物正常移动，但是不正常执行动画，人物会漂移；按89行那样写只摁WSAD中的一个按键人物正常移动，并且正常执行动画。

但是同时摁下WD或WA或SD或SA，人物都会漂移。