Rotate table on its edges like in Bloxorz

Hello! I'm trying to create a Bloxorz-like movement, but instead of a cuboid, I'm using a table. Everything works great until the table reaches this point, when it sinks through the plane.

The model was created directly in Unity, no third-party softwares were used, such as Blender. Here is the script in C# the table is using:

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 
 public enum Direction {
     North,
     South,
     East,
     West
 }
 
 public class TableMove : MonoBehaviour {
 
     private float rotationSpeed = 750f, totalRotation;
     private bool isMoving;
     private Direction rotationDirection;
     private Vector3 pivot, axis, scale;
 
     void Start () {
         isMoving = false;
         scale = transform.localScale / 2f;
     }
 
     void Update () {
         if (isMoving) {
             float deltaRotation = rotationSpeed * Time.deltaTime;
             if (totalRotation + deltaRotation >= 90f) {
                 deltaRotation = 90f - totalRotation;
                 isMoving = false;
             }
             if ((rotationDirection == Direction.West) || (rotationDirection == Direction.North))
                 transform.RotateAround (pivot, axis, deltaRotation);
             else transform.RotateAround (pivot, axis, -deltaRotation);
             totalRotation += deltaRotation;
         }
         else if (Input.GetKeyDown (KeyCode.W)) Rotate (Direction.North);
         else if (Input.GetKeyDown (KeyCode.A)) Rotate (Direction.West);
         else if (Input.GetKeyDown (KeyCode.S)) Rotate (Direction.South);
         else if (Input.GetKeyDown (KeyCode.D)) Rotate (Direction.East);
     }
 
     void Rotate (Direction direction) {
         rotationDirection = direction;
         isMoving = true;
         totalRotation = 0f;
         switch (rotationDirection) {
             case Direction.East:
                 pivot = transform.position + new Vector3 (scale.x, -scale.y, 0);
                 break;
             case Direction.West:
                 pivot = transform.position + new Vector3 (-scale.x, -scale.y, 0);
                 break;
             case Direction.North:
                 if (transform.localEulerAngles.x != 0) {
                     if (transform.localEulerAngles.x == -90) {
                         pivot = transform.position + new Vector3 (0, -scale.y, scale.z + 0.9f);
                     } else {
                         pivot = transform.position + new Vector3 (0, -scale.y, scale.z);
                     }
                 }
                 else
                     pivot = transform.position + new Vector3 (0, -scale.y - 0.9f, scale.z);
                 break;
             case Direction.South:
                 pivot = transform.position + new Vector3 (0, -scale.y, -scale.z);
                 break;
         }
         if ((rotationDirection == Direction.East) || (rotationDirection == Direction.West)) {
             axis = Vector3.forward;
             float temp = scale.x;
             scale.x = scale.y;
             scale.y = temp;
         } else {
             axis = Vector3.right;
             float temp = scale.z;
             scale.z = scale.y;
             scale.y = temp;
         }
     }
 }

Any help would be highly appreciated! :)

Sincerely,

Unity Passionate