Grabbing objects causes player object to tumble

Hello all. This is my first post, and I am just starting out.

I am working on an homage to Atari Adventure (learning purposes only), but I am running into a problem with replicating the 'grab by bumping into objects' mechanic. I have cobbled together a script that I am sure is very inefficient, but it works for the most part. The objects do attach, but once I detach them, my player object starts tumbling around like some momentum was stored or something. Any help would be greatly appreciated! :)

Here are the specs:

Player object (cube) Box Collider (w/material added to promote sliding rather than spinning) Rigidbody (all standard)

Item (cube) Box Collider (w/same material) + set to trigger

And here is my script:

 using UnityEngine;
 using System.Collections;
 
 public class PlayerMove1 : MonoBehaviour {
 
     public float speed;
     
     private Rigidbody rb;
 
     private bool hasObject = false;
 
     private GameObject theChild;
 
     private Vector3 offset;
 
     void Start ()
     {
         rb = GetComponent<Rigidbody>();
     }
     
     void FixedUpdate ()
     {
         float moveHorizontal = Input.GetAxis ("Horizontal");
         float moveVertical = Input.GetAxis ("Vertical");
         
         Vector3 movement = new Vector3 (moveHorizontal, 0.0f, moveVertical);
 
         rb.AddForce (movement * speed);
 
         if (Input.GetKeyDown(KeyCode.Space)){
             theChild.transform.parent = null;
             hasObject = false;
             theChild.GetComponent<Collider>().isTrigger = true;
         }
     }
     void OnTriggerEnter(Collider hitThis)
     {
         if (hitThis.CompareTag("Item") && !hasObject){
             //change scene
             offset = hitThis.transform.position - transform.position;
             hitThis.transform.position = transform.position + offset * 2;
             hitThis.transform.parent = this.transform;
             hitThis.isTrigger = false;
             hasObject = true;
             theChild = hitThis.gameObject;
         }
     }
 }