clamping player position while in cover

So, I'm trying to integrate a cover system, and so far i have it to the point where the player can lerp to the object, and walk along it's surface. But, I'm running into issues right now, because if once the player walks along the object, they can just keep walking beyond the edges of the cover object, which is, needless to say sort of a problem. I tried clamping the x and z positions of the player, creating an effective window that they can sort of walk in, and because the direction of movement is also limited, it seemed a fair attempt. But, when they hit the edge of that window, they slide along it like a collider I think, which causes the player to then be pushed into the cover object, but then my script resets the position to avoid having the player be displaced. That creates a very noticeable jitter at the edges of that walkable window. Secondly: I'm not sure how to detect the edges of a cover object, and I don't want to manually have to enter dimensions for every single object face that the player could ever want to take cover on. Here's what I have so far, and the problem right now lies in those last few lines of code about limiting the character to walking only behind the cover. Any help improving this code would be much appreciated.

 function restrictMovement()
 {
     //establishes normal reference to be applied to object later
     var normal : Vector3 = new Vector3 (0, 1, 0);
     //establishes tangnt vector based on the normal reference vector and the transform of the object
     var tangent : Vector3 = Vector3.Cross(normal, coverObject.transform.forward);
     
     //ensures no errors are acquired if the magnitude is 0
     if (tangent.magnitude == 0)
     {
         tangent = Vector3.Cross(normal, Vector3.up);
     }
     //can only move after lerp is done
     yield WaitForSeconds(lerpTime + 0.1);
     
     //adjust movement to respond to the player differently    
     fpsController.moveDirection =-Input.GetAxis("Horizontal") * tangent;
     fpsController.moveDirection = fpsController.moveDirection * fpsController.speed;
     
     //clamps player movement to size of object
     transform.position.x = Mathf.Clamp(transform.position.x, coverObject.transform.position.x - 3, coverObject.transform.position.x+3);
     transform.position.z = Mathf.Clamp(transform.position.z, coverObject.transform.position.z-3,coverObject.transform.position.z + 3);
 }