Comment 1 for bug 1549256

I investigated the issue by recompiling the QtQuick module and adding some debug info in qquickflickable.cpp

I added some debug in void QQuickFlickablePrivate::handleMouseMoveEvent(QMouseEvent *event)
(I only added qDebug, the extra lines are to show the context)

    if ((hMoved && !prevHMoved) || (vMoved && !prevVMoved))
        q->movementStarting();

    qint64 currentTimestamp = computeCurrentTime(event);
    qreal elapsed = qreal(currentTimestamp - (lastPos.isNull() ? lastPressTime : lastPosTime)) / 1000.;
    qDebug() << QString("Elapsed " % QString::number(elapsed) % " currentTimestamp " % QString::number(currentTimestamp)
             % " lastPos.isNull " % QString::number(lastPos.isNull()) % " lastPressTime " % QString::number(lastPressTime)
             % " lastPosTime " % QString::number(lastPosTime) % " vertical velocity " % QString::number(vData.velocity)
             % " horizontal velocity " % QString::number(hData.velocity));
    if (elapsed <= 0)
        return;

And I added some debug in the handleMouseReleaseEvent as well

    qDebug() << QString("Mouse release! Elapsed " % QString::number(elapsed) % " vertical velocity " % QString::number(vData.velocity)
                % " horizontal velocity " % QString::number(hData.velocity));
    qreal vVelocity = 0;
    if (elapsed < 100 && vData.velocity != 0.) {
        vVelocity = (QGuiApplicationPrivate::mouseEventCaps(event) & QTouchDevice::Velocity)
                ? QGuiApplicationPrivate::mouseEventVelocity(event).y() : vData.velocity;
    }

The resulting log is at http://pastebin.ubuntu.com/15196346/