Qwt shows old axes and titles on a new plot

Question

I am trying to use Qwt in my project. I need to draw a plot which can be replaced by another based on some conditions.

My widget is created with the following code:

QStackedWidget *stackedWidget = new QStackedWidget(ui->m_capacitancesWidget);

for(int i = 0; i < sensors; ++i) {
    QwtPlot *plot = new QwtPlot();
    m_capacitancesPlots.push_back(plot); // convenience vector for easy access to plots
    plot->setTitle(tr("Mutual capacitances"));
    plot->setCanvasBackground(Qt::white);
    plot->insertLegend(new QwtLegend());

    QwtPlotCurve *curve = new QwtPlotCurve();
    curve->setTitle(tr("Sensor %1").arg(1));
    curve->setPen(Qt::green, 1);
    curve->setRenderHint(QwtPlotItem::RenderAntialiased, true);
    curve->attach(plot);

    // actually I add another two curves which have some data, but I omit it in this snippet

    stackedWidget->addWidget(plot);
}

QVBoxLayout *layout = new QVBoxLayout;
layout->addWidget(stackedWidget);
ui->m_capacitancesWidget->setLayout(layout);

Here is my widget:

Sometimes I am loading new data and want to refresh the widget. Since there could be different number of sensors and so on, I call the following code to clean things up and then the same code above to create the view from scratch:

for(int i = 0; i < m_capacitancesPlots.size(); ++i)
    m_capacitancesPlots[i]->detachItems(QwtPlotItem::Rtti_PlotItem, true);

m_capacitancesPlots.clear();

if(ui->m_capacitancesWidget->layout())
    delete ui->m_capacitancesWidget->layout();

But after this, my widget looks like this:

Axes are doubled, titles are doubled. Plots seem to be ok, but when I draw the third one (green in legend), it's not visible. It seems that although QStackedWidget and QwtPlot are completely new, I see some cached old QwtPlot. How to properly clean my widget and draw new QwtPlot?