The QStackedWidget's Preferred vertical size policy made it request height equal to the tallest child  page. Without scrolling, this forced the dialog to grow beyond the screen.

The consequence is rather annoying, depending on WMs, the dialog cannot be moved up, nor resized, so options change cannot be accepted (or any action on the set of buttons at the bottom of the dialog, but blindly using keyboard).

A proper solution isn't trivial, as we need to add a scrollarea to ensure it doesn't happen.