Bug occurs when I done next steps: 0) create mainwindow with menu and qwebengineview as 1 of element sentral widget 1) load url to webengineview (in my case - it was local html file) 2) set focus to qwebengineview by mouse click 3) go to menu, open submenu and click any item 4) get assert.

My solution was catch focus in events to focusproxy widget of qwebenginewidget and change reason of event from Qt::PopupFocusReason to Qt::NoFocusReason. It works. But it is hack)