lerp works on (-6.5/y/z) but not on (+6.5/y/z)

for some reason my lerped transformation of my local position works on the one side (left[negative x-axis]) but not on the right side(positive-x-axis)

the target vector gets defined through as it should on both sides, as well as everything else except for the lerp!!! works fine without lerp.

I really don't get the problem and have no idea for a workaround, so please help! even with a workaround! If I switch from local- to worldposition I still got the same problem just the other way around!

 using UnityEngine;
 using System.Collections;
 
 public class wallrun : MonoBehaviour {
 
     public float currentxposition;
     public Rigidbody rb;
     public float xposition = 0f;
     bool endwallrun = false;
    public bool jumponwall = false;
     public float newlane;
     float ywallrun;
    public Vector3 targetposition;
 
     // Use this for initialization
     void Start () {
     
     }
 
     public void unlockZaxis()
     {
         rb.constraints = RigidbodyConstraints.None;
         newlane = 0;
     }
     public void resetlane()
     {
         float yposition = gameObject.transform.localPosition.y;
         float zposition = gameObject.transform.localPosition.z;
         transform.localPosition = new Vector3(xposition, yposition, zposition);
 
     }
 
     public void jumpOffWall()
     {
         endwallrun = false;
         Invoke("unlockZaxis",0f);
     }
 
     public void WallrunRight()
     {
         endwallrun = true;
         xposition = gameObject.transform.localPosition.x;    // sets "xposition" to the current lane-position
         float zposition = gameObject.transform.localPosition.z;    // maintain position while switching lanes
         float yposition = gameObject.transform.localPosition.y;    // maintain height while switching lanes
         ywallrun = yposition + 2.5f;
         Ray ray = new Ray(transform.position, transform.right);
         RaycastHit hit;
         if (Physics.Raycast(ray, out hit, 3) && Physics.Raycast(ray, out hit, 2) == false)
         {
             jumponwall = true;
             newlane = xposition + 1.5f;
             
         }
         else if (Physics.Raycast(ray, out hit, 2))
         {
             ;
         }
         endwallrun = false;
     }
     public void WallrunLeft()
     {
         endwallrun = true;
         xposition = gameObject.transform.localPosition.x;    // sets "xposition" to the current lane-position
         float zposition = gameObject.transform.localPosition.z;    // maintain position while switching lanes
         float yposition = gameObject.transform.localPosition.y;    // maintain height while switching lanes
         ywallrun = yposition + 2.5f;
         Ray ray = new Ray(transform.position, -transform.right);
         RaycastHit hit;
         if (Physics.Raycast(ray, out hit, 3) && Physics.Raycast(ray, out hit, 2) == false)
         {
             jumponwall = true;
             newlane = xposition - 1.5f;
            
         }
         else if (Physics.Raycast(ray, out hit, 2))
         {
             ;
         }
         endwallrun = false;
     }
 
     // Update is called once per frame
     void Update () {
         if(jumponwall==true)
         {
             
             currentxposition = gameObject.transform.localPosition.x;
             float currentzposition = gameObject.transform.localPosition.z;   
             float currentyposition = gameObject.transform.localPosition.y;
             targetposition = new Vector3(newlane, ywallrun, currentzposition);
             transform.localPosition = Vector3.Lerp(transform.localPosition, targetposition, Time.deltaTime * 2);
             rb.constraints = RigidbodyConstraints.FreezePositionY| RigidbodyConstraints.FreezeRotationZ;
             
             if (currentxposition<newlane + 0.5f|| currentxposition < newlane - 0.5f )
             {
 
                 //newlane = 0;
                 jumponwall = false;
                 
             }
            
                 Invoke("unlockZaxis", 4f);
                 Invoke("resetlane", 4.25f);
             
         }
 
     }
 }
 

the project is a onrail-runner with parcour elements ;)