Same here, with Delphi11,Windows 11.
After shrinking the form to it's minimum width, when you click the maximize square button (without resizing back the form to some larger width) , it maximizes without the ribbon controls.
In 64 bits it also happened that the form "tried" to maximize in height, but not in width (after some attempts and resizing I could maximize, but the first tries only made it taller). It happened once with 32 bits.
With a 1920x1080 monitor, almost all ribbon controls were gone. With a 2560x1440 monitor, all controls were gone.