Player character X rotation going haywire on game start

Hey all, so randomly my player characters rotation is messing with me. I was working on an orbit cam that I could rotate around the player on the Y axis depending on which key was pressed sort of like a Runescape deal. I added a dummy object(sphere), attached the camera to it and set the transform position of the dummy object to my player and then added the rotation script to the dummy, I successfully did this and everything was working perfect.

After a happy victory, I decided to attempt and correct the player falling over problem when it attempts to walk over a bump or incline (I'm using a custom thirdperson character) as freezing the rigidbody rotation constraints was not solving this issue. I attempted to mess around with Quaternion and freeze the rotation via script, unfortunately I am still a noob to all of this and had no idea what I was doing, I was able to freeze all 3 rotations and the player was staying upright while going up an incline, but unfortunately now the player would not turn on the Y axis when walking in different directions. So I deleted all my code relating to freezing the rotations and decided to tackle something else. This is when the issue started.

For a couple of game starts the player was doing fine just as it was when I finished the orbit cam setup, but now, every time I start the game, my players X-axis goes automatically to -90 and bounces around! (Even with the X constraint frozen via rigidbody), if I click around the map rapidly the player will eventually bounce back to standing upright, but even then the X axis is a bit touchy and he very slowly starts to fall over (WITH CONSTRAINTS FROZEN?) So my question is, is there a way I could freeze my players X and Z rotation indefinitely via script? as I attempted to do earlier with Quaternions and failed? or even at least correct this issue to where my player will once again stand upright. did me messing with Quaternions hard-code some kind of glitch?

My Code:

 using UnityEngine;
 using System.Collections;
 using UnityEngine.EventSystems;
 
 public class PlayerController : MonoBehaviour
 {
     public float speed = 6;
     public Rigidbody rb;
     public Animator anim;
 
     private Vector3 targetPosition;
     private bool isMoving;
 
     const int LEFT_MOUSE_BUTTON = 0;
 
     void Start ()
     {
 
         targetPosition = rb.transform.position;
         isMoving = false;
 
     }
 
     void Update()
     {
 
         if (Input.GetMouseButtonDown (LEFT_MOUSE_BUTTON))
             SetTargetPosition ();
 
         if (isMoving)
             MovePlayer();
 
         if (PointerOverUI())
          {
              targetPosition = transform.position;
              isMoving = false;
          }
          else
          {
              MovePlayer();
          } 
 
     }
 
     public bool PointerOverUI() // method for checking if pointer is over a UI
     {
         return UnityEngine.EventSystems.EventSystem.current.IsPointerOverGameObject();
     }
 
     void SetTargetPosition ()
     {
         Plane plane = new Plane (Vector3.up, rb.transform.position);
         Ray ray = Camera.main.ScreenPointToRay (Input.mousePosition);
         float point = 0f;
 
         if (plane.Raycast(ray, out point))
         {
             targetPosition = ray.GetPoint(point);
         }
 
         if (PointerOverUI()) // If the pointer is clicked over a UI, player will not go to clicked point
         {
             targetPosition = transform.position;
         }
         else // if the pointer is not over UI, then player will move
         {
             MovePlayer(); 
         }
 
         isMoving = true;
     }
 
     void MovePlayer ()
     {
             rb.transform.LookAt(targetPosition);
             rb.transform.position = Vector3.MoveTowards(transform.position, targetPosition, speed * Time.deltaTime);
 
         if (transform.position == targetPosition)
             isMoving = false;
 
         if (isMoving == false) {
             anim.SetInteger("Condition", 0);
             return;    
         } else {
             anim.SetInteger("Condition", 1);
         }
 
         Debug.DrawLine (transform.position, targetPosition, Color.red);
     }
 
 }

and my dummy object camera script, just in case that happened to have something to do with it:

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 
 public class RotateCamera : MonoBehaviour {
 
     public int speed = 150;
 
     public GameObject player;
 
     void Update()
     {
         Vector3 pos = player.transform.position;
         transform.position = pos;
 
         if (Input.GetKey(KeyCode.A)) // rotate camera left
             transform.Rotate(Vector3.up * speed * Time.deltaTime);
 
         if (Input.GetKey(KeyCode.D)) // rotate camera right
             transform.Rotate(-Vector3.up * speed * Time.deltaTime);
     }
 }

(I HAVE NO COMPILER/CONSOLE ERRORS)

I can't see anything that would affect my players rotation to the point to where he'd fall over, go haywire on the X-axis and ignore the rigidbody constraints? Then again, as i said, I am still a super noob, so any insight or help would be so much apreciated! thank you!