groundspeed info arrive period is too long in 1.1.3.1

I'm using the following code to obtain GPS data each second:

locationDataSource = QGeoPositionInfoSource::createDefaultSource(this);
if (locationDataSource)

{ locationDataSource->setPreferredPositioningMethods(QGeoPositionInfoSource::AllPositioningMethods); QObject::connect(locationDataSource, SIGNAL(positionUpdated(QGeoPositionInfo)), this, SLOT(positionUpdated(QGeoPositionInfo))); locationDataSource->startUpdates(); }

After updating to Symbian Anna and updating QtMobility component to revision 1.1.3.1, QGeoPositionInfo::GroundSpeed attribute of QGeoPositionInfo is arrive each 15 seconds or even more
GPS position arrives each second as defined
After rolling back QtMobility to 1.1.3 GroundSpeed arrives ones per second