Rigidbody +parenting +rotation +elevator = Player unwanted behavior(pushed away)

Hey Dev´s

I have problems with an elevator script or better with the "OnCollisionExit" function in it. Basically I parent the Player to the elevator with "OnCollisionEnter" and if the user makes an Input I unparent it and do a rotation, and this works so far.

But when I try to unparent with the "OnCollisionExit" the Player is pushed through the scene. I can reproduce this in OnCollisionEnter when activating "playerTransform.parent = null" at the end!

The problem is I need "OnCollisionExit" if the player is not longer on the elevator.

Any Ideas?

         //Elevator Script
         //
         /////////////////////////
         // Move the Elevator 
         //Start Point 
         var targetA : GameObject;
         //Finish Point 
         var targetB : GameObject;
         //Speed
         var speed : float = 0.1;
         //////////////////////////
         //
         // 
         //Code for moving the Elevator
         function FixedUpdate () 
            {
              var weight = Mathf.Cos(Time.time * speed * 2 * Mathf.PI) * 0.5 + 0.5;
              transform.position = targetA.transform.position * weight
              + targetB.transform.position * (1-weight);
            }
         //
         // If player enters the Elevator...
         function OnCollisionEnter(other : Collision)
          {
            //
            FPSWalker.grounded = true;  //This is not the standard FPSWalker Script, 
                                        //just the same name
            var playerTransform = other.transform;
            //Parent the player to the Elevator
            playerTransform.parent = transform;
             //
             //If User do this input unparent from Elevator
             if(Input.GetButtonDown("Rotate1"))
               {
                 playerTransform.parent = null;
               }
             //
             //If User do this input unparent from Elevator
             if(Input.GetButtonDown("Rotate2"))
               {
                 playerTransform.parent = null;
               }
                //
               //
               //playerTransform.parent = null;  //(1)if this is active, same error like the one in    OnCollisionExit
           }
     ///////////////////////////////////////////////////////
 //if OnCollision is active player is pushed around the scene 
  /*
     function OnCollisionExit(other : Collision)
       {
         var playerTransform = other.transform;
         playerTransform.parent = transform;
         playerTransform.parent = null;
             //Here no difference if FPSWalker.grounded = true or false
             //FPSWalker.grounded = false;
       }
 */
 ////////////////////////////////////////////////////