Click-and-Move System: Unit flies upward on slopes

Hello people. So, I'm working on a tactical strategy prototype and I was writing some code to get a unit to move towards a clicked point. Since this is my first time experimenting with click n' move systems, I ran into a lot of problems initially -even though the code is small- like having my unit stuck in my test plane. I'm prototyping using a simple cylinder as a unit and a plane as ground. While my code works perfectly on a level plane, the problem begins whenever I'm clicking at a slope or the top of a cube. Here's my code (spaced out for clarification):

 using UnityEngine;
 using System.Collections;
 
 public class MouseCharMovement : MonoBehaviour {
 
     public float testSpeed = 0.2f;
 
     bool hasHit = false;
 
     public int terrainMask = 1 << LayerMask.NameToLayer("testGround");
     public int playerMask = 1 << LayerMask.NameToLayer("Player");
 
     Vector3 currentPosition;
     Vector3 targetPosition;
 
     void Start () 
     {
         currentPosition = transform.position;    
         targetPosition = currentPosition;
         playerMask = ~playerMask;
     }
     
 
     void Update () 
     {    
         // Performs a cam-to-mouse Raycast every time the mouse button is pressed
         if(Input.GetButtonDown("Fire1"))
         {            
             // Ray to acommodate camera raycasting
             Ray mouseRay = Camera.main.ScreenPointToRay(Input.mousePosition);
             RaycastHit mouseHit;
 
             if(Physics.Raycast(mouseRay,out mouseHit,playerMask))
             {     
                 // Target is now the clicked position and a hit has been detected    
                 targetPosition = mouseHit.point;
                 hasHit = true;
             }
         }
 
 
 
         // If target is reached, slowly transform the object
         if (hasHit && ((currentPosition.x != targetPosition.x) && (currentPosition.z != targetPosition.z)))
         {    
             // Adds the object's center so as to keep it above ground
             Vector3 tempTarget = new Vector3(targetPosition.x,targetPosition.y + transform.position.y,targetPosition.z);
 
                 
             transform.position = Vector3.MoveTowards(transform.position,tempTarget,testSpeed);
             currentPosition = transform.position;
 
             // Check only for XY axes, ignore height
             if ((currentPosition.x == targetPosition.x) && (currentPosition.z == targetPosition.z))
             {
                 hasHit = false;
             }
 
 
         }
 
 
 
         Debug.Log("Transform Position: "+ transform.position);
         Debug.Log("Target Position: " + targetPosition);
         Debug.Log("Has Hit: "+ hasHit);
 
     }
 }

I'm testing by using the cylinder as the unit to which the script is attached to. A level plane set to origin represents level ground and a slightly rotated plane is put next to it to represent a slope. My unit moves perfectly on the level plane, but as soon as I click the slope, it starts flying in the air. I understand that this is happening because the code is constantly adding the unit's and slope's heights, and the problem isn't obvious in level ground simply because it's Y-component is zero. However, I included a test only for X-Z and still, it doesn't disable it. What am I missing here?

Thank you!