QtQuick ListView shows wrong number of rows on Windows

We have a large tree model containing all sorts of simulation data.

For easy access I wrote a proxy model which I set on different branches of this model. Because we have loads of role names I also filter the roles to the ones needed for the desired purpose.

This proxy model is displayed in a QML ListView with appropriate delegate. 

This list model shows the wrong number of rows.

In order to track this problem down I wrote a minimal example with only a very simple model which toggles the number of rows and the roleNames in a timer.  This is done in between beginResetModel() and endResetModel(). 

This should be a legal operation because it also occurs if I change the sourceModel() of a proxy model which is definitely a legal operation. Therefore I would expect correct display of the model data in my ListView.

But on Windows with Qt 6.7.3 VS 2019 as well as Qt 6.8.0 with VS 2022 I get twice the number of rows as myModel.rowCount() returns. See my attached screenshot.

Now please have a look into DummyModel.cpp (see attachment). If you un-comment line 13 (m_timer->stop) then the effect still occurs.

But if you instead change line 16 to m_timer->singleShot(true); then the ListView suddenly shows the correct number of rows!

This problem does NOT occur on Linux with Qt 6.7.2. (I don't have a newer Qt version on my linux box, sorry.)