Flask security doesn't throw any errors

Question

I'm trying to display the errors flask-security should generate when there's a failed login, or improper registration or whatever, but it really appears the errors are not even generated in my project.

I'm using a custom form helper display template that looks like this (my_render_field):

{{ field(class="w3-input hidden-print w3-white", **kwargs)|safe }}
{% for error in field.errors %}
    <div class="w3-panel w3-red w3-display-container">
        <span onclick="this.parentElement.style.display='none'"class="w3-button w3-red w3-large w3-display-topright">&times;</span>
            <h3>Error!</h3>
            <p> {{ error }}</p>
    </div>
{% endfor %}

I have this thing work for everything but the fields generated by flask-security. I have a custom login form that looks like this:

<form action="{{ url_for_security('login') }}" method="POST" name="login_form">
      {{ login_form.hidden_tag() }}
      {{ my_render_field(login_form.email, placeholder='Email') }}
      {{ my_render_field(login_form.password, placeholder='Password') }}
        <div>
      <input type="checkbox" class="w3-check" value="Remember"><label>{{ gettext('Remember Me') }}</label></input>
            </div>
      <input type="submit" class="w3-button w3-blue" value="Submit">
    </form>

The login form is defined like this:

from flask_security import LoginForm

@security.login_context_processor
def security_login_processor():
    """ Simple function to inject flask-security's LoginForm into my login_form 
    This function also generates the localised title """
    return dict(login_form=LoginForm(), title=gettext('Sign In'))

However, after making sure SECURITY_FLASH_MESSAGES is explicitly set to true, I try to include flashed messages like this:

{% with messages = get_flashed_messages(with_categories=true) %}
    {% if messages %}
        {% for category, message in messages %}
            <p> {{ category }} - {{ message }}</p>
        {% endfor %}
    {% endif %}
{% endwith %}

And I never get any output.

EDIT:

It now appears that the fields from LoginForm() don't have validators? When I use login_user_form in my view, it works as expected, but that means I can't use a modified form.