transform.position not adding correctly with a Vector3

Hello Community,
I’m trying to change the y and z axis of my player at the same time as the player move up and down. Problem is at first only the z axis is getting added and the y remains the same.
The following is in a function being called in my FixedUpdate() function. The player will move and if I look at my inspector, after I stop, the y and z are the same.
I am using the z axis later to help me calculate a jump as the z stays where the ground is and the y is where the player is but the code returns this same issue.

    Debug.Log("vertical: " + vertical);
    movement.Set(horizontal, vertical, vertical); // z axis is to place which character is in front
    
    movement = movement.normalized * speed * Time.deltaTime; // make sure player isn't passing max speed and doesn't move per frame
    Debug.Log("movement: " + movement);
    Debug.Log("player's first position: " + transform.position);
    transform.position += movement; // Move the player
    Debug.Log("player's updated position: " + transform.position);

For the first movement I do the Log Shows:
vertical: 1
movement: (0.0, 0.1, 0.1)
player’s first position: (-2.5, 0.0, 0.0)
player’s updated position: (-2.5, 0.0, 0.1)

Hard to tell what you are trying to do here. Is this for for 2D or 3D movement?

It looks like you need to do this:

2D
movement.Set(horizontal, vertical, 0); // z axis is to place which character is in front

3D
movement.Set(horizontal, 0, vertical); // z axis is to place which character is in front

You would change that 0 to whatever your jump functionality is to get the desired jump effect.