QSortFilterProxyModel subclass returns undefined records

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I have a Proxy class that inherits the QSortFilterProxyModel to enable filtering a model. The following is how the class behaves:

proxy.hpp:

class Proxy : public QSortFilterProxyModel
{
    Q_OBJECT

    // Q_PROPERTY
    Q_PROPERTY(bool filterStatus READ getFilterStatus WRITE setFilterStatus NOTIFY filterStatusChanged)
    Q_PROPERTY(bool sensitivityStatus READ getSensitivityStatus WRITE setSensitivityStatus NOTIFY sensitivityStatusChanged)
    Q_PROPERTY(QString filterValue READ getFilterValue WRITE setFilterValue NOTIFY filterValueChanged)
    Q_PROPERTY(QString roleText READ getRoleText WRITE setRoleText NOTIFY roleTextChanged)

public:
    explicit Proxy(QObject *parent = nullptr);
    ~Proxy();

    // Fields
private:
    bool m_FilterStatus;
    bool m_SensitivityStatus;
    QString m_FilterValue;
    QString m_RoleText;

    // Signals
signals:
    void filterStatusChanged();
    void sensitivityStatusChanged();
    void filterValueChanged();
    void roleTextChanged();

    // PUBLIC Methods
public:
    Q_INVOKABLE QVariantMap get(int proxyRow) const;

    // PRIVATE Methods
private:
    int mapToRole(const QString &role) const;

    // PUBLIC Getters
public:
    bool getFilterStatus() const;
    bool getSensitivityStatus() const;
    QString getFilterValue() const;
    QString getRoleText() const;

    // PUBLIC Setters
public:
    void setFilterStatus(bool newFilterStatus);
    void setSensitivityStatus(bool newSensitivityStatus);
    void setRoleText(const QString &newRoleText);
    void setFilterValue(const QString &newFilterValue);

    // OVERRIDES
protected:
    bool filterAcceptsRow(int sourceRow, const QModelIndex &sourceParent) const override;
};

proxy.cpp:

Proxy::Proxy(QObject *parent) :
    QSortFilterProxyModel(parent)
    , m_FilterStatus (true)
    , m_SensitivityStatus(true)
    , m_FilterValue("")
    , m_RoleText("")
{
#ifdef QT_DEBUG
    qDebug() << "objectName :" << this->objectName();
    qDebug() << "Arguments  :" << "None";
    qDebug() << "Log Output :" << "None";
#endif
}

Proxy::~Proxy()
{
#ifdef QT_DEBUG
    qDebug() << "objectName :" << this->objectName();
    qDebug() << "Arguments  :" << "None";
    qDebug() << "Log Output :" << "None";
#endif
}

QVariantMap Proxy::get(int proxyRow) const
{
    QModelIndex proxyIndex = index(proxyRow, 0);
    QModelIndex sourceIndex = mapToSource(proxyIndex);

    QVariantMap itemMap;

    const auto roles = roleNames();
    for (auto it = roles.constBegin(); it != roles.constEnd(); ++it)
    {
        itemMap.insert(
            QString::fromUtf8(it.value()),
            sourceModel()->data(sourceIndex, it.key())
        );
    }

    return (itemMap);
}

int Proxy::mapToRole(const QString &role) const
{
    int roleIndex = sourceModel()->roleNames().key(role.toUtf8(), -1);

    return (roleIndex);
}

bool Proxy::getFilterStatus() const
{
    return (m_FilterStatus);
}

bool Proxy::getSensitivityStatus() const
{
    return (m_SensitivityStatus);
}

QString Proxy::getFilterValue() const
{
    return (m_FilterValue);
}

QString Proxy::getRoleText() const
{
    return (m_RoleText);
}

void Proxy::setFilterStatus(bool newFilterStatus)
{
    if (m_FilterStatus == newFilterStatus)
    {
        return;
    }

    m_FilterStatus = newFilterStatus;
    emit filterStatusChanged();

    // Force filter to update:
    invalidateFilter();
}

void Proxy::setSensitivityStatus(bool newSensitivityStatus)
{
    if (m_SensitivityStatus == newSensitivityStatus)
    {
        return;
    }

    m_SensitivityStatus = newSensitivityStatus;
    emit sensitivityStatusChanged();

    m_SensitivityStatus == true ? setFilterCaseSensitivity(Qt::CaseSensitive) : setFilterCaseSensitivity(Qt::CaseInsensitive);

    // Force filter to update:
    invalidateFilter();
}

void Proxy::setFilterValue(const QString &newFilterValue)
{
    if (m_FilterValue == newFilterValue)
    {
        return;
    }

    m_FilterValue = newFilterValue;
    emit filterValueChanged();

    // Force filter to update:
    invalidateFilter();
}

void Proxy::setRoleText(const QString &newRoleText)
{
    if (m_RoleText == newRoleText)
    {
        return;
    }

    m_RoleText = newRoleText;
    emit roleTextChanged();

    // Force filter to update:
    invalidateFilter();
}

bool Proxy::filterAcceptsRow(int sourceRow, const QModelIndex &sourceParent) const
{
    if (m_FilterStatus == false)
    {
        return (true); // Accept all rows
    }

    if(m_FilterValue == "")
    {
        return (true); // Accept all rows
    }

    if(m_RoleText == "")
    {
        return (true); // Accept all rows
    }

    QString data = sourceModel()->data(
        sourceModel()->index(sourceRow, 0, sourceParent),
        mapToRole(m_RoleText)
    ).toString();

#ifdef QT_DEBUG
    qDebug() << "Data found: " << data;
#endif

    return (data == m_FilterValue);
}

I expose the classes via a context to QML:

int main(int argc, char *argv[])
{
    QGuiApplication app(argc, argv);

    QQmlApplicationEngine engine;

    Proxy *proxyModelName = new Proxy(&app);
    Proxy *proxyModelCity = new Proxy(&app);

    // Expose filters to QML via context property
    engine.rootContext()->setContextProperty("proxyModelName", proxyModelName);
    engine.rootContext()->setContextProperty("proxyModelCity", proxyModelCity);

    const QUrl url(QStringLiteral("qrc:/Model/main.qml"));
    QObject::connect(
        &engine,
        &QQmlApplicationEngine::objectCreated,
        &app,
        [url](QObject *obj, const QUrl &objUrl) {
            if (!obj && url == objUrl)
                QCoreApplication::exit(-1);
        },
        Qt::QueuedConnection);
    engine.load(url);

    return app.exec();
}

To test the functionality I created a test model in QML:

import QtQuick 2.15
import QtQuick.Controls 2.15
import QtQuick.Layouts 1.15

ApplicationWindow {
    id: window
    visible: true
    width: 800
    height: 600
    title: "Proxy Model Filter Test"

    // A ListModel with multiple items and roles.
    ListModel {
        id: myListModel
        ListElement { name: "Alice"; age: 30; city: "New York" }
        ListElement { name: "Bob"; age: 25; city: "San Francisco" }
        ListElement { name: "Charlie"; age: 30; city: "Boston" }
        ListElement { name: "Diana"; age: 40; city: "Chicago" }
        ListElement { name: "Eve"; age: 25; city: "Los Angeles" }
        ListElement { name: "Frank"; age: 30; city: "Boston" }
        ListElement { name: "George"; age: 35; city: "Seattle" }
        ListElement { name: "Hannah"; age: 28; city: "Boston" }
        ListElement { name: "Ian"; age: 32; city: "New York" }
        ListElement { name: "Jane"; age: 29; city: "San Francisco" }
        ListElement { name: "Kevin"; age: 45; city: "Chicago" }
        ListElement { name: "Laura"; age: 30; city: "Los Angeles" }
        ListElement { name: "Mike"; age: 33; city: "Seattle" }
        ListElement { name: "Nina"; age: 27; city: "New York" }
        ListElement { name: "Oliver"; age: 31; city: "Boston" }
        ListElement { name: "Paula"; age: 26; city: "Chicago" }
    }

    Component.onCompleted: {
        proxyModelCity.roleText = "city";
        proxyModelName.roleText = "name";
        proxyModelCity.sourceModel = myListModel;
        proxyModelName.sourceModel = proxyModelCity;
    }

    ColumnLayout {
        anchors.fill: parent
        spacing: 10

        RowLayout {
            spacing: 10

            // TextField for filtering by name.
            Label {
                text: "Name:"
                Layout.alignment: Qt.AlignVCenter
            }

            TextField {
                id: nameField
                placeholderText: "Enter name"
                Layout.fillWidth: true
                onTextChanged: {
                    // Update the filterRules: if empty, remove the name filter.
                    if (nameField.text.trim() === "") {
                        proxyModelName.filterValue = "";
                    } else {
                        proxyModelName.filterValue = nameField.text.trim();
                    }
                }
            }

            // ComboBox for filtering by city.
            Label {
                text: "City:"
                Layout.alignment: Qt.AlignVCenter
            }
            ComboBox {
                id: cityComboBox
                model: ["All", "New York", "San Francisco", "Boston", "Chicago", "Los Angeles", "Seattle"]
                Layout.preferredWidth: 150

                onCurrentTextChanged: {
                    if (cityComboBox.currentText === "All") {
                        proxyModelCity.filterValue = "";
                    } else {
                        proxyModelCity.filterValue = cityComboBox.currentText.trim();
                    }
                }
            }
        }

        // ListView to display the filtered items.
        ListView {
            id: listView
            Layout.fillWidth: true
            Layout.preferredHeight: 300
            model: proxyModelName

            delegate: Rectangle {
                width: listView.width
                height: 40
                border.width: 1

                Row {
                    anchors.verticalCenter: parent.verticalCenter
                    spacing: 10
                    Text { text: "Name: " + name; width: 150 }
                    Text { text: "Age: " + age; width: 50 }
                    Text { text: "City: " + city; width: 150 }
                    Button {
                        onClicked: {
                            // 'index' is provided by the delegate.
                            var itemData = proxyModelName.get(index);
                            console.log("Row " + index + " data:", itemData["name"]);
                            // This way you can pass the entire itemData map to something else.
                        }
                    }
                }
            }
        }
    }
}

The good news is that the filters work correctly in finding the records that I specify, but the problem is that along with the correct records come a bunch of other ones which are undefined or non-existent:

I don't understand what is causing this and would really appreciate some help.