setColumnHidden does not hide column

[mikrocat]

In my software I have a tableview with a model.
While runtime the model changes. Sometimes I want to hide columns, but after I changed the model a third time it does not work anymore.

void MonitorWindow::setColumnsHidden(bool hide){
    for (int i = 0; i < myTransducermodel->columnCount(); ++i){
        qDebug() << hide << i;
        ui->transducerTable->setColumnHidden(i, hide);
        qDebug() << "hidden?" << ui->transducerTable->isColumnHidden(i);
    }
 }
}

void MonitorWindow::setColumnsHidden(bool hide){
    for (int i = 0; i < myTransducermodel->columnCount(); ++i){
        qDebug() << hide << i;
        ui->transducerTable->setColumnHidden(i, hide);
        qDebug() << "hidden?" << ui->transducerTable->isColumnHidden(i);
    }
 }
}

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The Debug says:
true 0
hidden? false
true 1
hidden? false
true 2
hidden? false
true 3
hidden? false
...

Why is that? Do I miss something when I set a new model?

myTransducermodel->clearColumns();
 
....
 
ui->transducerTable->setModel(myTransducermodel);

myTransducermodel->clearColumns();

....

ui->transducerTable->setModel(myTransducermodel);

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void TransducerSetModel::clearColumns(){
    tableHeaders.clear();
}

void TransducerSetModel::clearColumns(){
    tableHeaders.clear();
}

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