How to setData in foreign key table of QSqlRelationalTableModel via QSortFilerProxyModel?

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The following situation exists:
An SQLite database with an N:M relationship. The whole thing is solved via a table between

Table: Deutscher_Pilzname

+----------------------------------+
| Id | Pilz_id | Deutscher_name_id |
+----------------------------------+
| 1  |   700   |         1         |
| 2  |    33   |         2         |
| .. |   ...   |        ...        |
+----------------------------------+

Table: Deutscher_Name

+----+----------------+
| Id | Deutscher_Name |
+----+----------------+
|  1 | Name_1         |
|  2 | Name_2         |
| .. | ...            |
+----+----------------+

Now I'm getting the data out via a QSqlRelationTableModel.

QSqlRelationalTableModel *DatabaseManager::germanFungusNameDataModel() const
{
    QSqlRelationalTableModel *model = new QSqlRelationalTableModel;
    model->setTable("Deutscher_Pilzname");
    model->setRelation(model->fieldIndex("Deutscher_name_id"), QSqlRelation("Deutscher_Name", "Id", "Name"));
    model->setJoinMode(QSqlRelationalTableModel::LeftJoin);
    model->setSort(2, Qt::AscendingOrder);
//    model->setEditStrategy(QSqlRelationalTableModel::OnManualSubmit);
    model->select();
    while (model->canFetchMore()) {
        model->fetchMore();
    }
    return model;
}

In the constructor of my mainwindow.cpp I create a subclassed QSortFilerProxyModel and set the source Model and set it to a QListView.

//QSqlRelationTableModel
mGermanFungusNameDataModel = mDatabaseManager->germanFungusNameDataModel();

//Subclassed QSortFilerProxyModel
mGermanNameDataFilter->setSourceModel(mGermanFungusNameDataModel);
mGermanNameDataFilter->sort(Column::GermanName);
mGermanNameDataFilter->setSortCaseSensitivity(Qt::CaseInsensitive);

//QListView
mGermanNameEditor->setModel(mGermanNameDataFilter);
mGermanNameEditor->setModelColumn(Column::GermanName);

Now I have created a QDialog where I cann change the text and after that I call this:

    const bool germanNameIsSelected = mGermanNameEditor->selectionModel()->hasSelection();
                QModelIndex index = mGermanNameEditor->currentIndex();
                QModelIndex sourceIndex = mGermanNameDataFilter->mapToSource(index);
                GermanNameEditor editor(this);
                if(germanNameIsSelected){
                    QString name = index.data().toString();
                    editor.setCurrentText(name);
                    editor.setModal(true);
                    const int type = editor.exec();
            
                    if(type == QDialog::Accepted){
                        QString changedName = editor.currentText();
                        auto value = sourceIndex.siblingAtColumn(2).data().toString();
            
                        while(mGermanFungusNameDataModel->relationModel(2)->canFetchMore()){
                            mGermanFungusNameDataModel->relationModel(2)->fetchMore();
                        }
                        qDebug() << "RowCount relation: " << mGermanFungusNameDataModel->relationModel(2)->rowCount();
                        for(int i=0 ;i<mGermanFungusNameDataModel->relationModel(2)->rowCount();i++){
                            const QModelIndex index = mGermanFungusNameDataModel->relationModel(2)->index(i, 1);
                            const QVariant data = index.siblingAtColumn(1).data();
                            if(data.toString() == value) {
                               qDebug() << "setData relationModel: " << mGermanFungusNameDataModel->relationModel(2)->setData(index, changedName, Qt::EditRole);
                               mGermanFungusNameDataModel->database().transaction();
                               qDebug() << "Submitall: " << mGermanFungusNameDataModel->submitAll();
                               mGermanFungusNameDataModel->database().commit();
                               break;
                            }
                        }

setData returns true and submitAll as well, but the whole thing is not changed. Neither in the GUI nor in the database. This is probably related to my subclassed QSortFilterProxyModel. I thought when the sourceModel is changed the QSortFilerProxyModel is updated automatically.

Does anyone have any idea?