GameObject not being added to list of GameObject

in the Vehicle_AI script:

    private void OnTriggerEnter(Collider other){
        ZoneVehicles triggerZone=other.GetComponent<ZoneVehicles>();
        triggerZone?.AddVehicle(this.gameObject);
    }

in the ZoneVehicle script:

    void Awake()
    {
        vehiclesInZone=new List<GameObject>();
    }
    public void AddVehicle(GameObject vehicle){
        vehiclesInZone.Add(vehicle);
        if(vehiclesInZone!=null)Debug.Log(vehiclesInZone[0]+" added");
        vehicle.GetComponent<Vehicle_AI>().UpdateNeighborsList(vehiclesInZone);
    }

Debug.Log in the AddVehicle is executed correctly with the correct vehicle, but then the vehicle is immediatly removed and the list becomes empty