Can someone reproduce this?

You will need a tablet, a device which ‘normal’ position is in lansdcape.

Set the desktop rotation to system default. (And enable the rotation in the device)

Rotate the tablet into portrait.

Go to lightning settings, desktop settings, any setting (just enter the settings)

Then go back to the desktop.

Now, in my tablet the whole desktop gets rotated, as in landscape, but the device is in portrait so it gets cutted.

To fix just rotate the tablet to landscape again.

Strange, very strange…and I discover it now…….I always use my tablet in landscape :P