why does update only run once?

No errors come on the console, but the script only runs once and then just stops. There is another script in this game that works fine.

This is the code:

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 
 public class movement_collision : MonoBehaviour
 {
     public Rigidbody rb;
     public float Xamount_to_move;
     public float Zamount_to_move;
     public float XLamount_move;
     public float YLamount_move;
 
     public float yaw;
 
     public static float yawspeed = 1;
     public static float acceleration = 125;
     public static float top_speed = 75;
     public static float throttlePunch = 7000;
 
     void FixedUpdate()
     {
         Xamount_to_move = Input.GetAxis("RightStickHorizontal");
         Zamount_to_move = Input.GetAxis("RightStickVertical");
         XLamount_move = Input.GetAxis("LeftStickHorizontal");
         YLamount_move = Input.GetAxis("LeftStickVertical") * -1;
 
         yaw = yaw + XLamount_move;
 
         rb.AddForce(Mathf.Sin(yaw * yawspeed) * Zamount_to_move * -acceleration * Time.deltaTime,
             0, Mathf.Cos(yaw  * yawspeed) * Zamount_to_move * -acceleration * Time.deltaTime, ForceMode.Impulse);
 
         rb.AddForce(Mathf.Cos(yaw * yawspeed) * Xamount_to_move * acceleration * Time.deltaTime,
             0, Mathf.Sin(yaw * yawspeed) * Xamount_to_move * -acceleration * Time.deltaTime, ForceMode.Impulse);
 
         if (YLamount_move > 0)
         {
             rb.AddForce(0, YLamount_move * throttlePunch * Time.deltaTime, 0);
         }
         if (YLamount_move < 0)
         {
             rb.AddForce(0, YLamount_move * 10000 * Time.deltaTime, 0);
         }
 
         rb.rotation = Quaternion.Euler(-Zamount_to_move * 24, yaw * (Mathf.PI * 2) * yawspeed, -Xamount_to_move * 24);
 
         rb.velocity = new Vector3(Mathf.Clamp(rb.velocity.x, -top_speed, top_speed),
                                   Mathf.Clamp(rb.velocity.y, -10000000, 10000000), 
                                   Mathf.Clamp(rb.velocity.z, -top_speed, top_speed));
         if (YLamount_move < 0.01)
         {
             if (YLamount_move > -0.01)
             {
                 rb.velocity = new Vector3(rb.velocity.x, rb.velocity.y / 1.075f, rb.velocity.z);
             }
         }
         if (Xamount_to_move < 0.01)
         {
             if (Xamount_to_move > -0.01)
             {
                 rb.velocity = new Vector3(rb.velocity.x / 1.05f, rb.velocity.y, rb.velocity.z);    
             }
         }
         if (Zamount_to_move < 0.01)
         {
             if (Zamount_to_move > -0.01)
             {
                 rb.velocity = new Vector3(rb.velocity.x, rb.velocity.y, rb.velocity.z / 1.05f);
             }
         }
         Debug.Log("frame complete");
     }
 }