QT QAbstractTableModel implement insertRows - c++

Question

I have an Impl of QAbstractTableModel, which has a vector<Item> items with all items of the table (one Item per Row)
int rowCount(..){ return items.size() }
QVariant data(const QModelIndex &index, int role){
Item i = items.at(index.row()));
switch(index.column()){
case 0: return i.zero;
(..)
}
}
Now I try to implement an add_row(Item i) Method:
void add_row(Item i){
int row = rowCount(QModelIndex())+1;
beginInsertRows(QModelIndex(), row, row);
items.push_back(i);
endInsertRows();
emit dataChanged(QModelIndex(), QModelIndex());
}
The QAbstractTableModel is instanciated in my widget:
MyQSortFilterProxyModel my_filter = new MyQSortFilterProxyModel();
MyTableModel* my_model = new MyTableModel(items, this);
my_filter->setSourceModel(my_model);
ui->my_table->setModel(my_filter);
and I like to add a new row like that:
my_model->add_item(item);
ui->my_table->reset();
This almost works fine with just one problem. The item is added to my table at the correct position and shows up correctly, but the last row always disappears.
Where am I doing something wrong? Why does the last row always disappear?!
Thanks!
Update:
void add_row(Item i){
int row = rowCount(QModelIndex())+1;
beginInsertRows(QModelIndex(), row, row);
items.push_back(i);
endInsertRows();
emit dataChanged(createIndex(0,0), createIndex(row,5));
}
this works but always returns the following error:
QSortFilterProxyModel: invalid inserted rows reported by source model
Without the FilterProxyModel everything works find. What am I missing in the FilterProxyModel?