Question How to fix character falling down stairs when not moving

I have made a character movement script and made stairs, i set the stairs to convex and walking up them is just fine but when i stand still on them my character falls down. Im using a rigidbody for the character. Is there any way to fix this? I can show my code if that helps

 

Code and Video of the issue is always helpful.
Also Collider Setup, Physics Materials

 

Code (CSharp):

1. using System.Collections;
2. using System.Collections.Generic;
3. using UnityEngine;
4. using TMPro;
5.  
6. public class PlayerMovement : MonoBehaviour
7. {
8.     [Header("Movement")]
9.     public float moveSpeed;
10.     public float gravity;
11.     public float groundDrag;
12.  
13.     public float jumpForce;
14.     public float jumpCooldown;
15.     public float airMultiplier;
16.     public float gravityHeight;
17.  
18.     bool readyToJump;
19.    
20.  
21.     [HideInInspector] public float walkSpeed;
22.     [HideInInspector] public float sprintSpeed;
23.  
24.     [Header("Keybinds")]
25.     public KeyCode jumpKey = KeyCode.Space;
26.  
27.     [Header("Ground Check")]
28.     public float playerHeight;
29.     public LayerMask whatIsGround;
30.     bool grounded;
31.    
32.     public Transform orientation;
33.  
34.     float horizontalInput;
35.     float verticalInput;
36.  
37.     Vector3 moveDirection;
38.  
39.     Rigidbody rb;
40.  
41.  
42.     private void Start()
43.     {
44.         rb = GetComponent<Rigidbody>();
45.         rb.freezeRotation = true;
46.  
47.         readyToJump = true;
48.     }
49.  
50.     private void Update()
51.     {
52.         if (!Physics.Raycast(transform.position, -transform.up, gravityHeight))
53.         {
54.             gravity = 18;
55.         }
56.  
57.         // ground check
58.             grounded = Physics.Raycast(transform.position, Vector3.down, playerHeight * 0.5f + 0.3f, whatIsGround);
59.  
60.         MyInput();
61.         SpeedControl();
62.  
63.         // handle drag
64.         if (grounded)
65.             rb.drag = groundDrag;
66.         else
67.             rb.drag = 0;
68.  
69.         if (Input.GetKey("left shift"))
70.         {
71.             moveSpeed = 19f;
72.         }
73.         else
74.         {
75.             moveSpeed = 15f;
76.         }
77.     }
78.  
79.     private void FixedUpdate()
80.     {
81.         MovePlayer();
82.         GetComponent<Rigidbody>().AddForce(Vector3.down * gravity * GetComponent<Rigidbody>().mass);
83.     }
84.  
85.     private void MyInput()
86.     {
87.         horizontalInput = Input.GetAxisRaw("Horizontal");
88.         verticalInput = Input.GetAxisRaw("Vertical");
89.  
90.         // when to jump
91.         if (Input.GetKey(jumpKey) && readyToJump && grounded)
92.         {
93.             readyToJump = false;
94.  
95.             Jump();
96.  
97.             Invoke(nameof(ResetJump), jumpCooldown);
98.         }
99.     }
100.  
101.     private void MovePlayer()
102.     {
103.         // calculate movement direction
104.         moveDirection = orientation.forward * verticalInput + orientation.right * horizontalInput;
105.  
106.         // on ground
107.         if (grounded)
108.             rb.AddForce(moveDirection.normalized * moveSpeed * 10f, ForceMode.Force);
109.  
110.         // in air
111.         else if (!grounded)
112.             rb.AddForce(moveDirection.normalized * moveSpeed * 10f * airMultiplier, ForceMode.Force);
113.     }
114.  
115.     private void SpeedControl()
116.     {
117.         Vector3 flatVel = new Vector3(rb.velocity.x, 0f, rb.velocity.z);
118.  
119.         // limit velocity if needed
120.         if (flatVel.magnitude > moveSpeed)
121.         {
122.             Vector3 limitedVel = flatVel.normalized * moveSpeed;
123.             rb.velocity = new Vector3(limitedVel.x, rb.velocity.y, limitedVel.z);
124.         }
125.     }
126.  
127.     private void Jump()
128.     {
129.         // reset y velocity
130.         rb.velocity = new Vector3(rb.velocity.x, 0f, rb.velocity.z);
131.  
132.         rb.AddForce(transform.up * jumpForce, ForceMode.Impulse);
133.     }
134.     private void ResetJump()
135.     {
136.         readyToJump = true;
137.     }
138. }

 

This doesn't tell us anything about the collider itself.
Are there steps? Is it sloped? etc.