QTableView inside QTabWidget does not show data

I have a QTabWidget, each tab contains a QTableView. The tableviews use QTableModels which reads data from an sqlite database.

The models are kept as member variables, so I don't think it's a scope problem (which is the most frequent problem I've found by searching for the issue).

Other db operations works: I tried populating / creating tables in the code, and those operation are correctly executed.

This is how I initialized the models and the views:

void AlisnagMainWindow::initModels(){
    people_model->setTable("people");
    people_model->setEditStrategy(QSqlTableModel::OnRowChange);
    people_model->select();
    people_model->setHeaderData(0, Qt::Horizontal, tr("Name"));
    people_model->setHeaderData(1, Qt::Horizontal, tr("Surname"));
    people_model->setHeaderData(2, Qt::Horizontal, tr("Phone"));
    people_model->setHeaderData(3, Qt::Horizontal, tr("Address"));

    items_model->setTable("items");
    items_model->setEditStrategy(QSqlTableModel::OnRowChange);
    items_model->setRelation(3, QSqlRelation("categories","id","name"));
    items_model->select();

    loans_model->setTable("loans");
    loans_model->setEditStrategy(QSqlTableModel::OnRowChange);
    loans_model->setRelation(0, QSqlRelation("items","id","name"));
    loans_model->setRelation(1, QSqlRelation("people","id","name"));
    loans_model->select();

    ui->peopleView->setModel(people_model);
    ui->peopleView->hideColumn(0);

    ui->itemsView->setModel(items_model);
    ui->itemsView->hideColumn(0);

    ui->loansView->setModel(loans_model);
    ui->loansView->hideColumn(0);

}

The database is loaded as follows:

bool AlisnagMainWindow::loadDB(const QString &filename)
{
    if(db.isOpen())
        db.close();
    db.setDatabaseName(filename);

    if( !db.open() ){
        QMessageBox::critical(this, tr("Error"),
                              tr("Could not open db %1").arg(filename),
                              QMessageBox::Ok);
        return false;
    }

    ui->statusBar->showMessage("DB successfully opened!");
    return true;

}

Then this is how is all combined:

void AlisnagMainWindow::openFile()
{
    QString filename = QFileDialog::getOpenFileName(this, tr("Choose DB file"),
                                                    ".", "*.db");
    loadDB(filename);

    initModels();
}

The file I'm opening has been populated externally. When I run the code, neither the data nor the headers are shown. Any insight?

Thanks in advance.