Diferent image sizes don't know why

[DuarteBarbosaPT]

Hi, I don't know why but I'm having this problem in Firefox

My code

                        <div class="item">
                            <div class="tile">
                                <div>
                                    <img role="imagem de capa" alt="imagem de capa" style="height:100%;" src="imagens/aesperadeummilagre.jpg" class="mx-auto d-block img-fluid"
                                        alt="placeholder">
                                </div>
                                <h3>A espera de um milagre</h3>
                                <p>content</p>
                            </div>
                        </div>

                        <div class="item">
                            <div class="tile">
                                <div>
                                    <img role="imagem de capa" alt="imagem de capa" style="height:100%;" src="imagens/condenacao.jpg" class="mx-auto d-block img-fluid"
                                        alt="placeholder">
                                </div>
                                <h3>A condenação</h3>
                                <p>content</p>
                            </div>
                        </div>