坂道に居る時に静止せず少しずつずれ下がる現象をなくしたい。

ジャンプしてオブジェクトに空中でぶつかってそのまま歩行キーを押しっぱなしにするとその空中の場所に静止してしまうのでカプセルコライダーのマテリアルをzero frictionを使って対処してための影響で坂道の上にいるときに下にずれ下がってるものと思います。これはどうすればいいのでしょうか？

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

public class Player : MonoBehaviour
{

    private float input_h;
    private float input_v;
    private Vector3 move;
    private Rigidbody rb;
    private float walk_speed;//移動速度
    private float run_speed;//歩き速度
    private float move_speed;//移動速度
    private const float gravity_force = -50.0f;
    private const float jump_force = 500.0f;
    private float gravity;//ジャンプの上下数値管理
    private Animator ani;
    AnimatorStateInfo nowState;
    private GameObject weapon;

    private bool isJump;
    private bool isGround;
    private bool rGround;
    private bool isSide;
    private bool isRun;



    /*外部系*/
    public bool isAttack;
    // Use this for initialization
    void Start()
    {
        walk_speed = 100.0f;
        run_speed = 200.0f;
        move_speed = walk_speed;


        weapon = GameObject.Find("Ethan/Hammer");
        isAttack = false;
        isJump = false;

        isGround = false;
        rGround = false;
        isSide = false;
        isRun = false;
        rb = GetComponent<Rigidbody>();
        ani = GetComponent<Animator>();
        nowState = ani.GetCurrentAnimatorStateInfo(0);
    }

    void anime_update()
    {
        /*アニメーション*/
        float speed = Mathf.Sqrt((move.x * move.x) + (move.z * move.z));
        ani.SetFloat("Move_Speed", speed);
       // Debug.Log(speed);

    }


    // Update is called once per frame
    void Update()
    {

        input_h = Input.GetAxis("Horizontal");
        input_v = Input.GetAxis("Vertical");
       
        Vector3 move_x = new Vector3();
        Vector3 move_y = new Vector3();

        move_y = Vector3.Scale(Camera.main.transform.forward, new Vector3(1, 0, 1)).normalized * input_v * move_speed;
        move_x = Camera.main.transform.right * input_h * move_speed;
        move = move_x + move_y;

        if (move != Vector3.zero)
        {
            transform.rotation = Quaternion.LookRotation(move.normalized);
        }

        anime_update();
        ray_update();

        //Debug.Log(rb.velocity);

        /*ジャンプ*/
        if (Input.GetKeyDown(KeyCode.Space))
        {
            if (rGround == true)
            {
                isJump = true;
            }
            
        }
        else
        {
           // Debug.Log("false");
           // isJump = false;
        }


        /*走るCtrlキー*/
        if (Input.GetKey(KeyCode.LeftControl))
        {
            move_speed = run_speed;
        }
        else
        {
            move_speed = walk_speed;

        }


        /*攻撃　left shift キー*/
        if (Input.GetKeyDown(KeyCode.LeftShift))
        {
            //isAttack = true;
            ani.SetTrigger("tAttack");


        }
        else
        {
           // isAttack = false;

        }

        /*
        if (ani.GetCurrentAnimatorStateInfo(0).IsName("Attack") == false)
        {
           isAttack = false;
//           Debug.Log("停止");


        }
        else
        {
            isAttack = true;
            Debug.Log("再生中");
            
        }
        */


        

        //Debug.Log("isAttack: " + isAttack);
        Debug.Log("rGround: " + rGround);
        Debug.Log("isJump: " + isJump);


    }


    void ray_update()
    {
        
        Ray ray = new Ray(transform.position, new Vector3(0,-1,0));
        RaycastHit rayhit;
        float range = 0.1f;
        Debug.DrawRay(ray.origin, ray.direction * range, Color.red);

        if(Physics.Raycast(ray,out rayhit,range))
        {
            rGround = true;
//            rb.velocity = Vector3.zero;

            //       Debug.Log("Ray hit!");
        }
        else
        {
           // Debug.Log("Ray ");

            rGround = false;
        }

        // Debug.Log(ray.direction);
    }

    void FixedUpdate()
    {
        if(isJump == true && rGround == true)
        {
        //    Debug.Log("jump !!!");
            move.y = jump_force;
            isJump = false;
            rGround = false;
           // rb.velocity = Vector3.zero;
        }
        else
        {
            move.y = gravity_force;
        }



        rb.AddForce(move);
    }



    private void OnCollisionEnter(Collision c)
    {
        /*
        if(c.gameObject.tag == "Coin")
        {
  //          Debug.Log("hit!!");
        }
        */
    }


    
    void a_start()
    {
        isAttack = true;
        Debug.Log("イベント発生!!!");
    }

    void a_end()
    {
        isAttack = false;
        Debug.Log("イベント終了");
    }


    private void Hit()
    {
        
    }
}