Unity 5: Game view - Run Time - SpaceBar Causing Issue - unity3d

Question

Game View- Camera Display
When I click the Space Bar for the player to jump, the Display drop down menu pops up and the player doesn't jump. However, the player can move upon all key presses.
Here's the information that I have:
1) Everything worked and functioned properly.
2) I added a health bar to my boss.
3) I created a second canvas (First canvas was for my Player's HP).
4) I made the Boss HP bar render mode: World Space.
5) I attached the canvas to the boss controller in the hierarchy as a child.
6) The code I use for Player Jump is Input.GetKeyDown(KeyCode.Space).
7) The mouse curser is inside the Game View whilst testing the SpaceBar Jump.
8) I'm developing in Unity 2018 5.3 2D mode.
Official Question('s):
1) Why does the Spacebar causing the camera display drop menu to appear?
2) How do I fix this?
Edit / Additional Content:
Here's my Jump script
public float jump1 = 5.0f;
private bool onGround;
//private bool dblJump; //Not implemented yet
public Rigidbody player;
void Start () {
player = GetComponent<Rigidbody>();
onGround = true;
}
// Update is called once per frame
void Update () {
if (onGround == true) {
if (Input.GetKeyDown(KeyCode.LeftShift))// KeyCode.Space
{
player.velocity = new Vector3(0, jump1, 0);
onGround = false;
// Debug.Log("The onGround is False");
}
}
}
Keep in mind that I have temporarily changed my jump to LeftShift. However, my problem persist with the space bar, even when I click it with left shift as my jump. SpaceBar seems to summon the drop down menu for the camera display. (I can't seem to catch the drop down menu with a screen shot because it goes away upon a click)
Also Note - I'm inside a class called PlayerJump : MonoBehavior.

Answer 1

It seems like it's a known issue with some versions of Unity 5.3, I have a few solutions you can try :
Drag you game window somewhere else in the editor
Enable the "Maximise on play" button
Attach this script to your drop-down element :
using UnityEngine;
using System.Collections;
using UnityEngine.UI;
using UnityEngine.EventSystems;
public class DropdownScript : MonoBehaviour, IPointerEnterHandler, IPointerExitHandler {
void Start()
{
dropDown = GetComponent<Dropdown>();
dropDown.interactable = false;
}
public void OnPointerEnter(PointerEventData ped)
{
dropDown.interactable = true;
}
public void OnPointerExit(PointerEventData ped)
{
dropDown.interactable = false;
}
}
Otherwise update you Unity version if it's not the latest release? I am not experiencing this issue but many other users are apparently.