PUT error: All object fields are null

Question

I have a user with id 3, a car with id 6 and I do a POST on the rental passing these 2 id’s, until then ok, the GET returns this

{
        "id": 5,
        "usuarioCliente": {
            "id": 3,
            "nome": "Arthur",
            "cpf": "281.590.328-89",
            "cnh": "35214349616",
            "telefone": "(61) 99805-2147",
            "email": "[email protected]",
            "senha": "1234",
            "perfil": "alugador",
            "endereco": {
                "id": 3,
                "logradouro": "Quadra SHPS Quadra 502",
                "bairro": "Setor Habitacional Pôr do Sol (Ceilândia)",
                "numero": 927,
                "complemento": " ",
                "cidade": "Brasília",
                "estado": "DF"
            }
        },
        "carro": {
            "id": 6,
            "usuarioRegistrador": {
                "id": 3,
                "nome": "Arthur",
                "cpf": "281.590.328-89",
                "cnh": "35214349616",
                "telefone": "(61) 99805-2147",
                "email": "[email protected]",
                "senha": "1234",
                "perfil": "alugador",
                "endereco": {
                    "id": 3,
                    "logradouro": "Quadra SHPS Quadra 502",
                    "bairro": "Setor Habitacional Pôr do Sol (Ceilândia)",
                    "numero": 927,
                    "complemento": " ",
                    "cidade": "Brasília",
                    "estado": "DF"
                }
            },
            "kmsRodados": 2.0,
            "documentoCarro": "3",
            "tipoCombustivel": "4",
            "marca": "Marca",
            "modelo": "Modelo",
            "placa": "bbb-1555",
            "valorCarro": 363636.0,
            "estaAlugado": true
        },
        "retirada": "2009-08-08",
        "entrega": "2019-08-05",
        "valor": 500.0
    }

When I make a PUT in rent, the idea is to change only the value and dates of withdrawal and delivery, the objects "car" and "user" must remain intact.

{
    "id": 5,
    "usuarioClienteId": 3,
    "carroId": 6,
    "retirada": "2000-01-01",
    "entrega": "2000-01-01",
    "valor": 33
}

When I run PUT, GET brings the right changes but all fields of the car object and user are null !!

{
    "id": 5,
    "usuarioCliente": {
        "id": 3,
        "nome": null,
        "cpf": null,
        "cnh": null,
        "telefone": null,
        "email": null,
        "senha": null,
        "perfil": null,
        "endereco": null
    },
    "carro": {
        "id": 6,
        "usuarioRegistrador": null,
        "kmsRodados": 0.0,
        "documentoCarro": null,
        "tipoCombustivel": null,
        "marca": null,
        "modelo": null,
        "placa": null,
        "valorCarro": 0.0,
        "estaAlugado": false
    },
    "retirada": "2000-01-01",
    "entrega": "2000-01-01",
    "valor": 33.0
}

What can I do to make it right?