setBinScene() creates a new QGraphicsScene each time which is never deleted. As each value change of the spinbox calls setBinScene(), your code piles up leaked QGraphicsScene objects. I'd suggest to avoid recreating the scene all together and just update a QGraphicsPixmapItem instead:
Initialize the scene (once):
QGraphicsScene *scene = new QGraphicsScene(this);
m_pixmapItem = new QGraphicsPixmapItem;
scene->addItem(m_pixmapItem);
ui->graphicsView->setScene(scene);
to set/update the image:
m_pixmapItem->setPixmap(pm);
ui->graphicsView->setSceneRect(0,0, bFile.ncols, bFile.nrows); //might want to avoid this one if the dimensions do not change