Bad widget rendering/crash when using QTreeWidget inside QGroupBox

I have a QTreeWidget inside a QGroupBox. I initialize the tree widget as in the example attached: list of filenames + icons retrieved through QFileIconProvider.
When I launch the application it is not properly rendered (see attached image bad.png): the headers or scrollbars are not shown/black, the items are not shown in the tree widget.
If I resize the windows I get in the output a lot of warnings about

[...]
QPaintDevice: Cannot destroy paint device that is being painted
QWidget::repaint: Recursive repaint detected
[...]

If I try to scroll the content (minimize to the minimum size the dialog and then drag the scrollbar), then I get a crash.

The problem seems caused by a combination of the font used (Courier New) and the QFileIconProvider. If I do not set any font or icon, then the widget is properly rendered (see good1.png with no font change or good2.png with no icon set in the tree widget).

This was not happening with Qt 5.4.1. It must be something changed in Qt 5.5.
I reproduced this problem on Windows 7. I'm using Microsoft Visual Studio 2013