Unity 2D Platformer: Crouching issues

I am having an issue currently with my C# Script for my 2D PLatformer made in Unity.
My issue is that when I press the crouch button for long enough(a second or less), my character falls through the floor and out of the map. I am stumped on how to get the sprite to not do that.

Thank you for the help! Code is posted below! (I posted the entire script for more clarification, however the issue is within the if statements regarding the "Crouch" input.)

For crouching, I have tried everything, I searched some tutorials, some in which I tried rewriting my entire script, but it got me no closer than I am now. For this I am expecting the sprite to not phase through the ground while crouching. There is not too many results with people asking about crouching in a 2d platformer.

using System.Collections;
using System.Collections.Generic;
using System.IO;
using UnityEngine;
public class PlayerMovement : MonoBehaviour
{
private Rigidbody2D rb;
private Animator anim;
private SpriteRenderer sprite;
private int jumpCount = 0;
private int maxJumps = 2;
private bool grounded = false;
private float dirX;
private new BoxCollider2D collider;
private Sprite crouching;
private Sprite standing;
private Vector2 crouchingSize;
private Vector2 standingSize;
private Vector2 crouchingOffset;
// Start is called before the first frame update
private void Start()
{
rb = GetComponent<Rigidbody2D>();
anim = GetComponent<Animator>();
sprite = GetComponent<SpriteRenderer>();
collider = GetComponent<BoxCollider2D>();
}
// Update is called once per frame
private void Update()
{
dirX = Input.GetAxisRaw("Horizontal");
float dirY = Input.GetAxisRaw("Vertical");
rb.velocity = new Vector3(dirX * 7f, rb.velocity.y, 0);
//Jump Button and double jump
if (Input.GetButtonDown("Jump") && jumpCount < maxJumps)
{
rb.velocity = new Vector3(rb.velocity.x, 14f, 0);
grounded = false;
jumpCount = jumpCount + 1;
}
if (grounded == true)
{
jumpCount = 0;
}
crouchingSize = new Vector2(1, 0.5f);
crouchingOffset = new Vector2(0, -0.25f);
standingSize = new Vector2(1, 1);
crouchingOffset = Vector2.zero;
//Start crouch
if (Input.GetButtonDown("Crouch"))
{
sprite.sprite = crouching;
collider.size = crouchingSize;
}
//Stop crouch
if (Input.GetButtonUp("Crouch"))
{
sprite.sprite = standing;
collider.size = standingSize;
}
UpdateAnimationState();
}
private void UpdateAnimationState()
{
dirX = Input.GetAxisRaw("Horizontal");
if (dirX > 0f)
{
anim.SetBool("running", true);
sprite.flipX = false;
}
else if (dirX < 0f)
{
anim.SetBool("running", true);
sprite.flipX = true;
}
else
{
anim.SetBool("running", false);
}
}
private void OnCollisionEnter2D(Collision2D collider)
{
if (collider.gameObject.tag == "Ground")
{
jumpCount = maxJumps;
grounded = true;
}
}
}

EDIT: Code block has been edited to reflect the solution to my question.

You seem to be transforming your player and then adding force to it's rigid body, which might cause clipping if the force factor is too big. What kind of 2D game are you trying to implement? In 2D you'd usually just want to scale down the collider object and change the sprite to a crouching one.

public sprite crouching;
public sprite standing;
public vector2 crouchingSize;
public vector2 standingSize;
.........
......
....
private void Update() 
{
if (Input.GetButtonDown("Crouch"))
{
SpriteRenderer.sprite = crouching;
Collider.size = crouchingSize;
}
//Stop crouch
if (Input.GetButtonUp("Crouch"))
{
SpriteRenderer.sprite = standing
Collider.size = standingSize;
}
}

I think a better approach would be to change the size of the collider and its offset. Changing the offset to the right amount makes sure you shrink the collider around the desired pivot point, something that Unity does not allow out of the box.

Let's assume that your character uses a box collider 2d, and when crouching your collider's size on the y-axis shrinks by 50%. In order to make sure that the collider doesn't float, we need to change the collider offset by negative 25% of your initial collider's size. (this will scale the collider around the pivot point at the feet of the character/ the bottom of the collider)
Ex. Size: (1, 1), Offset (0, 0) -> Size: (1, 0.5f); Offset (0, -0.25f).
The code would look something like this:

crouchingSize = new Vector2(1, 0.5f);
crouchingOffset = new Vector2(0, -0.25f);
standingSize = new Vector2(1, 1);
crouchingOffset = Vector2.zero;
if (Input.GetButtonDown("Crouch"))
{
SpriteRenderer.sprite = crouching;
Collider.size = crouchingSize;
Collider.offset = crouchingOffset;
}
if (Input.GetButtonUp("Crouch"))
{
SpriteRenderer.sprite = standing
Collider.size = standingSize;
Collider.offset = standindOffset;
}