Correct Normal alignment while keeping heading rotation from NavMeshAgent?

Hey guys, I have a cow. This cow should only rotate on the local x-axis regarding the normal of the terrain. And it should use the y-axis from the NavMeshAgent the rotate the heading of the cow.

So far my code looks like this and it works 95% of the time. But sometimes the cow sticks its head into the terrain. Basically flipping the local x-axis value. How can I improve this code?

Setup: Parent Empty(NavMeshAgent, BehaviorCow.cs) -> Cow Mesh + LOD

 using UnityEngine;
 using UnityEngine.AI;
 
 public class BehaviorCow : MonoBehaviour
 {
     //states 0 idle, 1 walk, 2 turn left, 3 turn right
     int animatorState;
 
     Vector3 target;
 
     public Terrain terrain;
     NavMeshAgent agent;
 
     void Start()
     {
         agent = GetComponent<NavMeshAgent>();
     }
 
     // Update is called once per frame
     void Update()
     {
         if (Input.GetKey(KeyCode.Mouse0)) {
             RaycastHit hit;
             Ray ray = Camera.main.ScreenPointToRay(Input.mousePosition);
             if (terrain.GetComponent<Collider>().Raycast(ray, out hit, Mathf.Infinity))
             {
                 target = hit.point;
 
                 agent.SetDestination(target);
 
                 Debug.Log(target);
             }
         }
 
         rotateToNormal(target);
     }
 
     void rotateToNormal(Vector3 destination)
     {
         float y = transform.localRotation.eulerAngles.y;
 
         Vector3 terrainSize = terrain.terrainData.size;
         Vector3 normal = terrain.terrainData.GetInterpolatedNormal(transform.position.x / terrainSize.x, transform.position.z / terrainSize.z);
 
         Debug.Log(normal);
 
         transform.localRotation = Quaternion.FromToRotation(Vector3.up, normal);
 
         transform.localRotation = Quaternion.Euler(transform.localRotation.eulerAngles.x, y, 0);
 
     }
 }