TestVerifier does not work on Ubuntu

Testing the indicators example and the monitor on the VirtualBox Ubuntu 20.04.

Seems that window capture is not working as expected but it takes the screenshot from the entire screen capture instead of window offset:

 QImage screenshot = qApp->screens().at(0)->grabWindow(
 QDesktopWidget().winId(),
 region.region().x(),
 region.region().y(),
 region.region().width(),
 region.region().height()).toImage();

where region.width=64,height=64,x=54, y=37
The output is the screenshot.png

The expected result is marked red to the actual_screenshot.png.