Why does my CharacterController Immediately Drop When Falling from an Object?

Hello!

I'm currently building a basic FPS, and I'm coming across a very peculiar problem.

I have found a way to make my player (built with the CharacterController) jump up and down and it works really well and everything, but I seem to come across a problem when I drop down from an object, such as a building. I can jump up and down with no problem from the building, but when I just drop down without jumping, my CharacterController just immediately falls down really fast.

Here's my Controller.cs code (used for moving the player):

 using UnityEngine;
 using System.Collections;
 
 public class Controller : MonoBehaviour {
 
     public float moveSpeed;
     public float mouseSpeed;
     private float lastMouseSpeed;
 
     public Camera playerCamera;
     public CharacterController player;
 
     private float sprintSpeed;
     private float originalMoveSpeed;
     public static bool sprinting = false;
 
     public float jumpHeight;
     public bool jumping = false;
     private float verticalVelocity;
 
     /* Locks the cursor in place and gets the CharacterController for manipulation. */
     void Start() {
         if (player == null) player = GetComponent<CharacterController>();
         sprintSpeed = moveSpeed * 1.8f;
         originalMoveSpeed = moveSpeed;
         lastMouseSpeed = mouseSpeed;
         Screen.lockCursor = true;
     }
 
     /* Enables player and NPC movement. */
     void Update() {
         // The key movements, (forward, backwards, side-to-side, etc).
         float forward = Input.GetAxis("Forward") * moveSpeed;
         float side = Input.GetAxis("Side") * moveSpeed;
 
         // The mouse movements.
         float rotationSide = Input.GetAxis("Mouse X") * mouseSpeed;
         float rotationForward = Input.GetAxis("Mouse Y") * mouseSpeed;
         transform.Rotate(0, rotationSide, 0);
         playerCamera.transform.Rotate(-rotationForward, 0, 0);
 
         if (Input.GetButton("Sprint")) {
             sprinting = true;
             moveSpeed = sprintSpeed;
         } else {
             moveSpeed = originalMoveSpeed;
             sprinting = false;
         }
 
         verticalVelocity += Physics.gravity.y * Time.deltaTime;
 
         if (player.isGrounded && Input.GetButtonDown("Jump")) {
             verticalVelocity = jumpHeight;
             jumping = true;
         } else {
             jumping = false;
         }
 
         Vector3 movement = new Vector3(side, verticalVelocity, forward);
 
         // As long as the game isn't paused, move and whatnot.
         if (EscapeMenu.paused != true) {    
             movement = GetLookout() * movement;
             player.Move(movement * Time.deltaTime);
         }
     }
 
     /* Returns the rotation (the mouse look) for processing. */
     Quaternion GetLookout() {
         return transform.rotation;
     }
 
     /* Returns the lastMouseSpeed. (Used for inventory and escape menu) */
     public float getLastMouseSpeed() {
         return lastMouseSpeed;
     }
 
     /* Sets the mouse speed. (Potential for options) */
     public void setMouseSpeed(float passedMouseSpeed) {
         this.mouseSpeed = passedMouseSpeed;
     }
 }