setProperty does not refresh immediatly with QString (?) as input value

Using qml engine from nelson language, I want to create a message box:

a=msgbox('fdddddddddddddd')
a =

[QObject] - size: 1x1

buttons: QFlags<QPlatformDialogHelper::StandardButton>
children: handle 1x1
className: QQuickPlatformMessageDialog
detailedText: QString
flags: QFlags<Qt::WindowType>
informativeText: QString
modality: Qt::WindowModality WindowModal
objectName: QString
parentWindow: QWindow* handle
result: int 0
text: QString fdddddddddddddd
title: QString '
visible: bool true

--> a.text='blabla'
--> a.text

'blabla'

BUT text of the message box is not updated (display is always 'fdddddddddddddd').
To be updated, It requires to force visibility
a.visible = false; a.visible = true

a.text = 'blabla' as a.visible = true
do in C++ code :
qobj->setProperty(wstring_to_utf8(propertyName).c_str(), v)
with v a QVariant v = QString('blabla')

Please notice that it works perfectly in Qt 5 on all platforms (linux, macos, windows)

Help will be appreciate