QTableWidget selection rectangle does not disappear even after editing is finished - c++

Question

I am implementing a QTableWidget, the selection rectangle seems not to be disappearing even after I finish editing and change my selection to other cells.
Below is a screenshot of the QTableWidget.
Below is the code for constructing the tablewidget, rows are added dynamically via a QPushButton:
{
setObjectName(obj_name);
layout = new QVBoxLayout();
table = new QTableWidget(this);
table->verticalHeader()->setVisible(false);
table->verticalHeader()->setDefaultSectionSize(20);
table->setFixedWidth(180);
table->setColumnCount(3);
table->setColumnWidth(0,75);
table->setColumnWidth(1, 75);
table->setColumnWidth(2, 25);
QStringList header = { "Tag", "Threshold" ,""};
table->setHorizontalHeaderLabels(header);
table->horizontalHeader()->setSectionResizeMode(QHeaderView::Fixed);
add = new QPushButton("+", this);
add->setObjectName("btn_threshold_add");
layout->addWidget(table);
layout->addWidget(add);
setLayout(layout);
connect(add, SIGNAL(clicked()), this, SLOT(add_row()));
}
Below is the code for add_row() SLOT, triggers when user clicked the add button:
void TagThresholdWidget::add_row()
{
int row = table->rowCount();
QPushButton *del = new QPushButton("-", table);
table->insertRow(row);
table->setCellWidget(row, 2, del);
connect(del, SIGNAL(clicked()), this, SLOT(remove_row()));
}
Anyone has any clue to how to solve this problem? Its seems like a Qt graphical paint bug to me