Odd Behavior with my Drag and Drop Code

Hey so I just started working on a drag and drop construction system, where the user can choose a structure and click and drag the position and length of the wall he is creating(think age of empires wall system) so far the drag and drop works well enough for isolated segments of walls, but anytime I try building off an already instantiated wall, the wall segment gets destroyed 80% of the time, and the rest works about 30% of the time, which confuses me on why my code would work so unreliably. Here's the class I use to create structures

 class CreateStructure extends MonoBehaviour
 {
     
     //test Prefab
     public var testSegment:GameObject;
     public var testConnector:GameObject;
     
     //Start and finish Locations of mouse drag
     var startPos:Vector3;
     var endPos:Vector3;
 
     //Build Camera
     var topCam:Camera;
         
     function Start()
     {
         topCam = GameObject.FindGameObjectWithTag("Build Camera").camera;
         testSegment = AssetDatabase.LoadAssetAtPath("Assets/Prefabs/WallSection1.prefab", GameObject);
         testConnector = AssetDatabase.LoadAssetAtPath("Assets/Prefabs/WallConnector1.prefab",GameObject);
     }
 
     function Update()
     {
         //when mouse clicked down, store starting position
         if(Input.GetMouseButtonDown(0))
         {
             startPos = FindLocation();
         }
         
         //when mouse button released, store ending position
         if(Input.GetMouseButtonUp(0))
         {
             endPos = FindLocation();
             CalculateAndPlace(startPos, endPos, testSegment);
         }
     }
     
 
     
     
     
     function FindLocation() : Vector3
     {
         //raycast based on mouse location
         var ray : Ray = topCam.ScreenPointToRay (Input.mousePosition);
         var hit : RaycastHit;
         if(Physics.Raycast(ray, hit))
         {
             //if no structures returned from raycast, return point
             if(hit.transform.tag == "Ground")
                 return hit.point;
                 
             //if structure returned, remove that structure    
             if(hit.transform.tag == "Small Wall" || hit.transform.tag == "Wall Connector")
             {
                 return ReplaceWall(hit.transform.gameObject);
             }
         }
         return hit.point;
     }
     
     
     
     
     function CalculateAndPlace(p1 : Vector3, p2 : Vector3, seg: GameObject)
     {
         //Create a ray long the path of the two points starting at startPos
         var temp:GameObject = new GameObject();
         temp.transform.position = p1;
         temp.transform.LookAt(p2);
         var directionRay : Ray = new Ray(p1, temp.transform.forward);
         
         //calculate distance between p1 and p2
         var distance :float = Vector3.Distance(p1,p2);
         
         //calculate number structures to be placed
         var numberOfStructures : int;
         var segmentLength = seg.renderer.bounds.size.z;
         numberOfStructures = distance / segmentLength;
         
         
         //place structures along the directionRay
         for(var i : int = 0; i <= numberOfStructures; i++)
         {
             PlaceStructure(directionRay.GetPoint(segmentLength * i), temp, seg);
         }
     }
     
     
     
     
     function PlaceStructure(position : Vector3, tempObj: GameObject, seg : GameObject)
     {
         Instantiate(seg, position, tempObj.transform.rotation);
     }
     
     //replace wall With connector prefab
     function ReplaceWall(obj : GameObject) : Vector3
     {
         //store obj components
         var tempTras :Vector3= obj.transform.position;
         var tempRot :Quaternion = obj.transform.rotation;
         
         //raise translate up 10 so raycast wont be below the ground
         tempTras.y += 10;
         
         //store ray to return
         var point : Vector3;
         
         //destroy object so raycast wont hit it
         Destroy(obj);
         
         //raycast to find position
         var hit : RaycastHit;
         if(Physics.Raycast(obj.transform.position, Vector3.down, hit))
         {
             point =  hit.point;
         }
         //instantiate the wall connector prefab
         Instantiate(testConnector, obj.transform.position, obj.transform.rotation);
         //return the raycast position
         return point;
 
     }
 }

Anyone have any ideas whats wrong with my code or a better system for drag and drop all together?