Enemy direction going crazy after collision

Well, this is my first time here friends! I wrote a simple code for moving an enemy. But when he collides with anything he seems to lose direction (following the player).

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 
 public class Mouthless_Behaviour : MonoBehaviour 
 {
     public Transform target;
     public float rotationSpeed = 0.1f;
     public float movementSpeed = 1.0f;
 
     // Use this for initialization
     void Start () 
     {
         
     }
     
     // Update is called once per frame
     void Update () 
     {
         if (target != null)
         {
             transform.position += transform.forward * Time.deltaTime * movementSpeed;
 
             var rotation = Quaternion.LookRotation (target.position - transform.position);
             transform.rotation = Quaternion.Slerp (transform.rotation, 
                                                      rotation, Time.deltaTime * rotationSpeed);
         }
     }
 }

If he collides with anything he change his direction and stop following the player. Here a GIF from this issue: Here!