From screenshot it's hard to tell if ubiquity is running from the live session (e.g. Try $distro -> then launch ubiquity) or from ubiquity-dm (e.g. Install $distro straight away). Potentially window decorators can be wrong/different in one or both cases and possibly it needs to be fixed in multiple places.
As far as I remember we should not have maximize,resize,minimize buttons anywhere.
From screenshot it's hard to tell if ubiquity is running from the live session (e.g. Try $distro -> then launch ubiquity) or from ubiquity-dm (e.g. Install $distro straight away). Potentially window decorators can be wrong/different in one or both cases and possibly it needs to be fixed in multiple places.
As far as I remember we should not have maximize, resize, minimize buttons anywhere.