Issue with character movement and collision using Physics2D.Raycast.

Hey guys, I've gotten this bug multiple times in the past trying to create a snap-movement game.

In the shot bellow you can see that the character is at (-7, 0) and attempting to move to (-6, 0).

This is my current script to handle movement:

 using UnityEngine;
 using System.Collections;
 
 public class PlayerMovement : MonoBehaviour {
     
     Vector3 pos;
     public float speed = 1.5f;
     private int collisionLayers = 7 << 8;
 
     void Start () {
         pos = transform.position;
     }
 
     void FixedUpdate () {
         if(Input.GetKey(KeyCode.A) && transform.position == pos) {
             CheckCollision(pos + Vector3.left);
         }
         if(Input.GetKey(KeyCode.D) && transform.position == pos) {
             CheckCollision(pos + Vector3.right);
         }
         if(Input.GetKey(KeyCode.W) && transform.position == pos) {
             CheckCollision(pos + Vector3.up);
         }
         if(Input.GetKey(KeyCode.S) && transform.position == pos) {
             CheckCollision(pos + Vector3.down);
         }
 
         transform.position = Vector3.MoveTowards(transform.position, pos, Time.deltaTime * speed);
     }
 
     void CheckCollision(Vector3 destination){
         Debug.Log (transform.position);
         Debug.Log (destination);
         RaycastHit2D hit = Physics2D.Raycast (transform.position, destination, 1f, collisionLayers);
         if (hit.collider == null) {
             pos = destination;
         } else {
             Debug.Log (hit.collider.gameObject + ": (" + hit.collider.transform.position.x + ", " + hit.collider.transform.position.y + ")");
         }
     }
 };

Expected response:

• Using Raycasting2D a line is drawn between one point and another, if the line comes into contact with any colliders it can be saved as a 'hit'.

• When drawing a line from the character's position (-7, 0) to (-6,0) there should be no collision taking place.

• The character may then continue movement to (-6, 0) "one tile to the right"

What is happening:

• When attempting to move into non-border tiles movement works perfectly

• Sometimes the character will not be able to move to a non-border tile if the character is next to a border tile.

What I think may be wrong:

In my code I have Physics2D.Raycast (transform.position, destination, 1f, collisionLayers); due to my very limited knowledge on how this Raycast works I can assume that I'm using the 3rd argument for distance incorrectly.

Each tile is one world unit so I assumed that the distance I would like to measure is 1f.

I've been working all day on this (and a few other days on a similar project with the same issue) with no luck to finding something similar online. This is my first time posting only for code questions so I hope I haven't left out any important details.

 CheckCollision(pos + Vector3.left, Vector3.left);
 void CheckCollision(Vector3 destination, Vector3 direction){
          Debug.Log (transform.position);
          Debug.Log (destination);
          RaycastHit2D hit = Physics2D.Raycast (transform.position, direction, 1f, collisionLayers);
          if (hit.collider == null) {
              pos = destination;
          } else {
              Debug.Log (hit.collider.gameObject + ": (" + hit.collider.transform.position.x + ", " + hit.collider.transform.position.y + ")");
          }
      }