Slerpy Spider Won't Behave (Chaining Slerps)

Hey all,

I'm having problems getting my script to switch between two slerps depending on the state of a bool.

I've got a spider that swings from "Start" to point "End" along an arc. Start and End are both public Transforms that can be set through the inspector and I've put in two empty game objects (A and B) that have been placed in the scene (at (0,0,0) and (10,0,0).

If A→B is true, then the spider slerps towards point B.

If the distance between A and B drops beneath a certain point (I've tried a few values) then the spider slerps back from B to A. Problem is that while A→B works fine, once the B→A bool kicks in, the spider darts between points A and B (linearly) within the span of a frame and then continues to dart in a straight line between the two points.

Here is the code.

 using UnityEngine;

using System.Collections;

public class spiderTest : MonoBehaviour {

 public Transform start;
 public Transform end;
 
 public bool startToFinish;
 public bool finishToStart;
 
 public float speed;
 public float distance;
 
 GameObject spider;
 public GameObject A;
 public GameObject B;
 
 Vector3 spiderPos;
 Vector3 startPos;
 Vector3 endPos;
 
 // Use this for initialization
 void Start () 
 {
     spider = this.gameObject;
     
     startPos = start.transform.position;
     endPos = end.transform.position;
     
     startToFinish = true;
     finishToStart = false;
     
     speed = 0.1f;
     transform.position = start.position;
     //transform.position = end.position;
 }
 
 // Update is called once per frame
 void Update () 
 {
     
     if(startToFinish == true)
     {
         Vector3 center = start.position + end.position * 0.5f;
         center -= new Vector3(0,-1,0);
         Vector3 startRelCenter = start.position - center;
         Vector3 endRelCenter = end.position - center;
         
         distance = Vector3.Distance(transform.position, end.transform.position);
         if(distance >= 0.1)
         {
             transform.position = Vector3.Slerp(startRelCenter, endRelCenter, Time.time * speed);
             transform.position += center;
         }
         if(distance <= 0.1)
         {
             ResetA();
         }
     
     }
     
     if (finishToStart == true)
     {
         Vector3 center = (start.position + end.position) * 0.5f;
         center -= new Vector3(0,-1,0);
         Vector3 startRelCenter = end.position - center;
         Vector3 endRelCenter = start.position - center;
         
         distance = Vector3.Distance(transform.position, start.transform.position);
         if(distance > 0.1)
         {
             transform.position = Vector3.Slerp(startRelCenter, endRelCenter, Time.time * speed);
             transform.position += center;
         }
         if(distance <= 0.1)
         {
             ResetB();
         }
     }
 }
 
 void ResetA()
 {
     if(startToFinish == true)
     {
         startToFinish = false;
         transform.position = end.position;
         distance = 0; 
         finishToStart = true;        
     } 
 }
 
 void ResetB()
 {
     if(finishToStart == true)
     {
         finishToStart = false;
         transform.position = start.position;
         distance = 0;
         startToFinish = true;
     }
 }

}

Can you see where I'm going wrong? Is there a way to make the spider slerp back from B to A?

(On a side note, I did think about handling the whole thing through the physics engine via a hinge joint chain, but at this point, it seems like handling it through scripts would fit the project better.)

Thanks for your time!