Reproduction:

• create a QGraphicsView 'myView' with an movable QGraphicsItem on it (i.e. with flag QGraphicsItem::ItemIsMovable)
• scroll (manually) in a manner so that the item covers view position (0,0)
• call QScroller::scroller(myView)->scrollTo(...)

→ nothing happens

Reason is (see Qt source 5.9.6):

call QScroller::scrollTo
→ call !d->prepareScrolling(QPointF())
→ a QScrollPrepareEvent is sent
→ the QScrollPrepareEvent is received by QAbstractScrollArea::event():

    case QEvent::ScrollPrepare:
    {
        QScrollPrepareEvent *se = static_cast<QScrollPrepareEvent *>(e);
        if (d->canStartScrollingAt(se->startPos().toPoint())) {
            ...

→ canStartScrollingAt is called with position QPointF() == (0,0):

        QGraphicsItem *childItem = view->itemAt(startPos);
        if (childItem && (childItem->flags() & QGraphicsItem::ItemIsMovable))
            return false;

→ return false

→ so the call '!d->prepareScrolling(QPointF())' in QScroller::scrollTo retuns false, and no scrolling occurs

I think the solution should make a difference between 1) software scroll (i.e. a call of QScroller::scrollTo) and 2) a user scroll per mouse. The test 'QAbstractScrollAreaPrivate::canStartScrollingAt' makes only sense for case 2).