WebEngineView proxy not work

hi, I set a authenticate http proxy for the QtWebEngine's example(quicknanobrowser) from the page QtWebEngine/NetWork (https://wiki.qt.io/QtWebEngine/Network), but not pass the username and password.

then when i visit a web page, the authentication request dialog is opening. At this moment, not input the username and password immediately. After 2 minutes input the right username and password, click login button. proxy login success, but cannot access the web page,and the web page shows timeout page.

at once the authentication request dialog open, input the username and password and login, the web page can access correct.

what's wrong with the authenticate http proxy when login 2 minutes later?